diff --git a/docs/commonmark.mdx b/docs/commonmark.mdx
index 8ea4ea86..b6aa6437 100644
--- a/docs/commonmark.mdx
+++ b/docs/commonmark.mdx
@@ -5,6 +5,8 @@ description: "Learn how to use Phiki with The PHP League's CommonMark library."
 
 If you're using `league/commonmark` to parse and render Markdown in your PHP project, you can easily integrate Phiki using our custom extension.
 
+## Usage
+
 ```php
 use League\CommonMark\Environment\Environment;
 use League\CommonMark\Extension\CommonMark\CommonMarkCoreExtension;
@@ -57,3 +59,43 @@ $environment
         'dark' => Theme::GithubDark, // [!code ++]
     ])); // [!code ++]
 ```
+
+### Highlighting and focusing lines
+
+You can highlight and focus lines in your code blocks using special annotations in the code block's info string.
+
+```md
+```php {2,4-8}{3}
+```
+
+The first set of braces represents the lines to highlight, while the second set represents the lines to focus on.
+
+In this example, line 2 will be highlighted, as well as lines 4 through 8. Line 3 will then be focused.
+
+If you only want to focus lines, you can use an empty set of braces for the highlighted lines:
+
+```md
+```php {}{3}
+```
+
+#### Sample CSS
+
+Phiki does not style the highlighted or focused lines by default, so you will need to add your own CSS.
+
+You can use the following sample CSS to get started:
+
+```css
+pre.phiki code .line.highlight {
+    background-color: hsl(197, 88%, 94%);
+}
+
+.shiki.focus .line:not(.focus) {
+    transition: all 250ms;
+    filter: blur(2px);
+}
+
+.shiki.focus:hover .line {
+    transition: all 250ms;
+    filter: blur(0);
+}
+```
diff --git a/src/Adapters/CommonMark/CodeBlockRenderer.php b/src/Adapters/CommonMark/CodeBlockRenderer.php
index 642c6e8a..4ba19171 100644
--- a/src/Adapters/CommonMark/CodeBlockRenderer.php
+++ b/src/Adapters/CommonMark/CodeBlockRenderer.php
@@ -7,9 +7,11 @@
 use League\CommonMark\Node\Node;
 use League\CommonMark\Renderer\ChildNodeRendererInterface;
 use League\CommonMark\Renderer\NodeRendererInterface;
+use Phiki\Adapters\CommonMark\Transformers\MetaTransformer;
 use Phiki\Grammar\Grammar;
 use Phiki\Phiki;
 use Phiki\Theme\Theme;
+use Phiki\Transformers\Meta;
 
 class CodeBlockRenderer implements NodeRendererInterface
 {
@@ -27,8 +29,13 @@ public function render(Node $node, ChildNodeRendererInterface $childRenderer)
 
         $code = rtrim($node->getLiteral(), "\n");
         $grammar = $this->detectGrammar($node);
+        $meta = new Meta(markdownInfo: $node->getInfoWords()[1] ?? null);
 
-        return $this->phiki->codeToHtml($code, $grammar, $this->theme)->withGutter($this->withGutter)->toString();
+        return $this->phiki->codeToHtml($code, $grammar, $this->theme)
+            ->withGutter($this->withGutter)
+            ->withMeta($meta)
+            ->transformer(new MetaTransformer)
+            ->toString();
     }
 
     protected function detectGrammar(FencedCode $node): Grammar|string
diff --git a/src/Adapters/CommonMark/Transformers/MetaTransformer.php b/src/Adapters/CommonMark/Transformers/MetaTransformer.php
new file mode 100644
index 00000000..f57f551c
--- /dev/null
+++ b/src/Adapters/CommonMark/Transformers/MetaTransformer.php
@@ -0,0 +1,95 @@
+<?php
+
+namespace Phiki\Adapters\CommonMark\Transformers;
+
+use Phiki\Phast\Element;
+use Phiki\Support\Arr;
+use Phiki\Transformers\AbstractTransformer;
+
+class MetaTransformer extends AbstractTransformer
+{
+    protected array $highlights = [];
+
+    protected array $focuses = [];
+
+    public function preprocess(string $code): string
+    {
+        $this->parse();
+
+        return $code;
+    }
+
+    public function line(Element $span, array $tokens, int $index): Element
+    {
+        if (in_array($index + 1, $this->highlights, true)) {
+            $span->properties->get('class')->add('highlight');
+        }
+
+        if (in_array($index + 1, $this->focuses, true)) {
+            $span->properties->get('class')->add('focus');
+        }
+
+        return $span;
+    }
+
+    protected function parse(): void
+    {
+        if (! $this->meta->markdownInfo) {
+            return;
+        }
+
+        [$highlights, $focuses] = array_pad(
+            explode(
+                '}{',
+                rtrim(ltrim($this->meta->markdownInfo, '{'), '}'),
+                2
+            ),
+            2,
+            null
+        );
+
+        if (! $highlights && ! $focuses) {
+            return;
+        }
+
+        $highlights = array_map(
+            fn(array $part) => count($part) > 1 ? $part : $part[0],
+            array_map(
+                fn(string $part) => array_map(fn(string $number) => intval($number), explode('-', trim($part))),
+                explode(',', $highlights)
+            )
+        );
+
+        foreach ($highlights as $part) {
+            if (is_array($part)) {
+                $this->highlights = array_merge($this->highlights, range($part[0], $part[1]));
+            } else {
+                $this->highlights[] = $part;
+            }
+        }
+
+        $this->highlights = array_unique($this->highlights);
+
+        if (! $focuses) {
+            return;
+        }
+
+        $focuses = array_map(
+            fn(array $part) => count($part) > 1 ? $part : $part[0],
+            array_map(
+                fn(string $part) => array_map(fn(string $number) => intval($number), explode('-', trim($part))),
+                explode(',', $focuses)
+            )
+        );
+
+        foreach ($focuses as $part) {
+            if (is_array($part)) {
+                $this->focuses = array_merge($this->focuses, range($part[0], $part[1]));
+            } else {
+                $this->focuses[] = $part;
+            }
+        }
+
+        $this->focuses = array_unique($this->focuses);
+    }
+}
diff --git a/src/Contracts/TransformerInterface.php b/src/Contracts/TransformerInterface.php
index d718ad53..d4823af5 100644
--- a/src/Contracts/TransformerInterface.php
+++ b/src/Contracts/TransformerInterface.php
@@ -6,6 +6,7 @@
 use Phiki\Phast\Root;
 use Phiki\Token\HighlightedToken;
 use Phiki\Token\Token;
+use Phiki\Transformers\Meta;
 
 interface TransformerInterface
 {
@@ -59,4 +60,9 @@ public function token(Element $span, HighlightedToken $token, int $index, int $l
      * Modify the HTML output after the AST has been converted.
      */
     public function postprocess(string $html): string;
+
+    /**
+     * Supply the meta object to the transformer.
+     */
+    public function withMeta(Meta $meta): void;
 }
diff --git a/src/Output/Html/PendingHtmlOutput.php b/src/Output/Html/PendingHtmlOutput.php
index 2132dc49..2f228ec2 100644
--- a/src/Output/Html/PendingHtmlOutput.php
+++ b/src/Output/Html/PendingHtmlOutput.php
@@ -15,6 +15,7 @@
 use Phiki\Token\Token;
 use Phiki\Transformers\Decorations\DecorationTransformer;
 use Phiki\Transformers\Decorations\LineDecoration;
+use Phiki\Transformers\Meta;
 use Psr\SimpleCache\CacheInterface;
 use Stringable;
 
@@ -34,6 +35,8 @@ class PendingHtmlOutput implements Stringable
 
     protected int $startingLineNumber = 1;
 
+    protected Meta $meta;
+
     /**
      * @param  array<string, ParsedTheme>  $themes
      */
@@ -102,6 +105,13 @@ public function startingLine(int $lineNumber): self
         return $this;
     }
 
+    public function withMeta(Meta $meta): self
+    {
+        $this->meta = $meta;
+
+        return $this;
+    }
+
     public function toString(): string
     {
         return $this->__toString();
@@ -153,6 +163,14 @@ public function __toString(): string
             return $this->cache->get($cacheKey);
         }
 
+        if (! isset($this->meta)) {
+            $this->meta = new Meta();
+        }
+
+        foreach ($this->transformers as $transformer) {
+            $transformer->withMeta($this->meta);
+        }
+
         [$code] = $this->callTransformerMethod('preprocess', $this->code);
         [$tokens] = $this->callTransformerMethod('tokens', call_user_func($this->generateTokensUsing, $code, $this->grammar));
         [$highlightedTokens] = $this->callTransformerMethod('highlighted', call_user_func($this->highlightTokensUsing, $tokens, $this->themes));
diff --git a/src/Transformers/AbstractTransformer.php b/src/Transformers/AbstractTransformer.php
index 188ad379..0cd23b6f 100644
--- a/src/Transformers/AbstractTransformer.php
+++ b/src/Transformers/AbstractTransformer.php
@@ -10,6 +10,11 @@
 
 class AbstractTransformer implements TransformerInterface
 {
+    /**
+     * The meta information.
+     */
+    protected Meta $meta;
+
     /**
      * Modify the code before it is tokenized.
      */
@@ -87,4 +92,12 @@ public function postprocess(string $html): string
     {
         return $html;
     }
+
+    /**
+     * Store the meta object.
+     */
+    public function withMeta(Meta $meta): void
+    {
+        $this->meta = $meta;
+    }
 }
diff --git a/src/Transformers/Meta.php b/src/Transformers/Meta.php
new file mode 100644
index 00000000..02a11f82
--- /dev/null
+++ b/src/Transformers/Meta.php
@@ -0,0 +1,10 @@
+<?php
+
+namespace Phiki\Transformers;
+
+readonly class Meta
+{
+    public function __construct(
+        public ?string $markdownInfo = null,
+    ) {}
+}
diff --git a/tests/.pest/snapshots/Adapters/CommonMark/PhikiExtensionTest/it_understands_the_info_string.snap b/tests/.pest/snapshots/Adapters/CommonMark/PhikiExtensionTest/it_understands_the_info_string.snap
new file mode 100644
index 00000000..c6ad6aaa
--- /dev/null
+++ b/tests/.pest/snapshots/Adapters/CommonMark/PhikiExtensionTest/it_understands_the_info_string.snap
@@ -0,0 +1,2 @@
+<pre class="phiki language-php github-dark" data-language="php" style="background-color: #24292e;color: #e1e4e8;"><code><span class="line highlight"><span class="token" style="color: #f97583;">class</span><span class="token"> </span><span class="token" style="color: #b392f0;">A</span><span class="token"> </span><span class="token">{</span><span class="token">}</span><span class="token">
+</span></span></code></pre>
diff --git a/tests/.pest/snapshots/Unit/CommonMark/PhikiExtensionTest/it_can_be_configured_using_environment_config_array.snap b/tests/.pest/snapshots/Unit/CommonMark/PhikiExtensionTest/it_can_be_configured_using_environment_config_array.snap
deleted file mode 100644
index ad8b8e1d..00000000
--- a/tests/.pest/snapshots/Unit/CommonMark/PhikiExtensionTest/it_can_be_configured_using_environment_config_array.snap
+++ /dev/null
@@ -1,2 +0,0 @@
-<pre class="phiki language-php github-light" data-language="php" style="background-color: #fff;color: #24292e;"><code><span class="line"><span class="token" style="color: #d73a49;">class</span><span class="token"> </span><span class="token" style="color: #6f42c1;">A</span><span class="token"> </span><span class="token">{</span><span class="token">}</span><span class="token">
-</span></span></code></pre>
diff --git a/tests/Adapters/CommonMark/PhikiExtensionTest.php b/tests/Adapters/CommonMark/PhikiExtensionTest.php
index e9505480..b08aadfa 100644
--- a/tests/Adapters/CommonMark/PhikiExtensionTest.php
+++ b/tests/Adapters/CommonMark/PhikiExtensionTest.php
@@ -4,6 +4,7 @@
 use League\CommonMark\Extension\CommonMark\CommonMarkCoreExtension;
 use League\CommonMark\MarkdownConverter;
 use Phiki\Adapters\CommonMark\PhikiExtension;
+use Phiki\Tests\Fixtures\UselessTransformer;
 use Phiki\Theme\Theme;
 
 it('registers renderers', function () {
@@ -47,3 +48,21 @@ class A {}
 
     expect($generated)->toMatchSnapshot();
 });
+
+it('understands the info string', function () {
+    $environment = new Environment;
+
+    $environment
+        ->addExtension(new CommonMarkCoreExtension)
+        ->addExtension(new PhikiExtension('github-dark'));
+
+    $markdown = new MarkdownConverter($environment);
+
+    $generated = $markdown->convert(<<<'MD'
+    ```php {0-10}
+    class A {}
+    ```
+    MD);
+
+    expect($generated)->toMatchSnapshot();
+});
diff --git a/tests/Adapters/CommonMark/Transformers/MetaTransformerTest.php b/tests/Adapters/CommonMark/Transformers/MetaTransformerTest.php
new file mode 100644
index 00000000..ec27df69
--- /dev/null
+++ b/tests/Adapters/CommonMark/Transformers/MetaTransformerTest.php
@@ -0,0 +1,166 @@
+<?php
+
+it('can highlight a single line', function () {
+    $output = markdown(<<<'MD'
+    ```php {1}
+    class A {}
+    ```
+    MD);
+
+    expect($output)->toContain('<span class="line highlight">');
+});
+
+it('can highlight a range of lines', function () {
+    $output = markdown(<<<'MD'
+    ```php {1-2}
+    class A {}
+    function b() {}
+    ```
+    MD);
+
+    expect(substr_count($output, '<span class="line highlight">'))->toBe(2);
+});
+
+it('can highlight multiple lines', function () {
+    $output = markdown(<<<'MD'
+    ```php {1,3}
+    class A {}
+    function b() {}
+    $a = new A();
+    ```
+    MD);
+
+    expect(substr_count($output, '<span class="line highlight">'))->toBe(2);
+});
+
+it('can highlight multiple ranges of lines', function () {
+    $output = markdown(<<<'MD'
+    ```php {1-2,4}
+    class A {}
+    function b() {}
+    $a = new A();
+    function c() {}
+    ```
+    MD);
+
+    expect(substr_count($output, '<span class="line highlight">'))->toBe(3);
+});
+
+it('can focus a single line', function () {
+    $output = markdown(<<<'MD'
+    ```php {}{2}
+    class A {}
+    function b() {}
+    ```
+    MD);
+
+    expect($output)->toContain('<span class="line focus">');
+});
+
+it('can focus a range of lines', function () {
+    $output = markdown(<<<'MD'
+    ```php {}{1-2}
+    class A {}
+    function b() {}
+    ```
+    MD);
+
+    expect(substr_count($output, '<span class="line focus">'))->toBe(2);
+});
+
+it('can focus multiple lines', function () {
+    $output = markdown(<<<'MD'
+    ```php {}{1,3}
+    class A {}
+    function b() {}
+    $a = new A();
+    ```
+    MD);
+
+    expect(substr_count($output, '<span class="line focus">'))->toBe(2);
+});
+
+it('can focus multiple ranges of lines', function () {
+    $output = markdown(<<<'MD'
+    ```php {}{1-2,4}
+    class A {}
+    function b() {}
+    $a = new A();
+    function c() {}
+    ```
+    MD);
+
+    expect(substr_count($output, '<span class="line focus">'))->toBe(3);
+});
+
+it('can highlight and focus lines', function () {
+    $output = markdown(<<<'MD'
+    ```php {1,3}{2}
+    class A {}
+    function b() {}
+    $a = new A();
+    ```
+    MD);
+
+    expect(substr_count($output, '<span class="line highlight">'))->toBe(2);
+    expect(substr_count($output, '<span class="line focus">'))->toBe(1);
+});
+
+it('ignores invalid line numbers', function () {
+    $output = markdown(<<<'MD'
+    ```php {0,4,5}{0,4,5}
+    class A {}
+    function b() {}
+    ```
+    MD);
+
+    expect(substr_count($output, '<span class="line highlight">'))->toBe(0);
+    expect(substr_count($output, '<span class="line focus">'))->toBe(0);
+});
+
+it('ignores invalid ranges', function () {
+    $output = markdown(<<<'MD'
+    ```php {2-1,3-2}{2-1,3-2}
+    class A {}
+    function b() {}
+    ```
+    MD);
+
+    expect(substr_count($output, '<span class="line highlight">'))->toBe(0);
+    expect(substr_count($output, '<span class="line focus">'))->toBe(0);
+});
+
+it('can highlight and focus the same line', function () {
+    $output = markdown(<<<'MD'
+    ```php {2}{2}
+    class A {}
+    function b() {}
+    ```
+    MD);
+
+    expect(substr_count($output, '<span class="line highlight focus">'))->toBe(1);
+});
+
+it('ignores non-numeric input', function () {
+    $output = markdown(<<<'MD'
+    ```php {a,b}{c,d}
+    class A {}
+    function b() {}
+    ```
+    MD);
+
+    expect(substr_count($output, '<span class="line highlight">'))->toBe(0);
+    expect(substr_count($output, '<span class="line focus">'))->toBe(0);
+});
+
+it('ignores empty input', function () {
+    $output = markdown(<<<'MD'
+    ```php {}{}
+    class A {}
+    function b() {}
+    ```
+    MD);
+
+    expect(substr_count($output, '<span class="line highlight">'))->toBe(0);
+    expect(substr_count($output, '<span class="line focus">'))->toBe(0);
+});
diff --git a/tests/Fixtures/UselessTransformer.php b/tests/Fixtures/UselessTransformer.php
index 05085c4f..b34a8a35 100644
--- a/tests/Fixtures/UselessTransformer.php
+++ b/tests/Fixtures/UselessTransformer.php
@@ -6,8 +6,10 @@
 use Phiki\Phast\Element;
 use Phiki\Phast\Root;
 use Phiki\Token\HighlightedToken;
+use Phiki\Transformers\AbstractTransformer;
+use Phiki\Transformers\Meta;
 
-class UselessTransformer implements TransformerInterface
+class UselessTransformer extends AbstractTransformer
 {
     public $preprocessed = false;
 
@@ -89,4 +91,9 @@ public function postprocess(string $html): string
 
         return $html;
     }
+
+    public function meta(): Meta
+    {
+        return $this->meta;
+    }
 }
diff --git a/tests/Pest.php b/tests/Pest.php
index 601eab89..dee21290 100644
--- a/tests/Pest.php
+++ b/tests/Pest.php
@@ -1,5 +1,9 @@
 <?php
 
+use League\CommonMark\Environment\Environment;
+use League\CommonMark\Extension\CommonMark\CommonMarkCoreExtension;
+use League\CommonMark\MarkdownConverter;
+use Phiki\Adapters\CommonMark\PhikiExtension;
 use Phiki\Grammar\Grammar;
 use Phiki\Grammar\GrammarRepository;
 use Phiki\Grammar\ParsedGrammar;
@@ -46,3 +50,12 @@ function highlight(array $tokens, array $theme): array
 
     return (new Phiki)->tokensToHighlightedTokens($tokens, $theme);
 }
+
+function markdown(string $input, Theme $theme = Theme::GithubLight): string
+{
+    $environment = new Environment();
+    $environment->addExtension(new CommonMarkCoreExtension)->addExtension(new PhikiExtension($theme));
+    $converter = new MarkdownConverter($environment);
+
+    return $converter->convert($input)->getContent();
+}
diff --git a/tests/Unit/PendingHtmlOutputTest.php b/tests/Unit/PendingHtmlOutputTest.php
index cdd44517..9d7eba81 100644
--- a/tests/Unit/PendingHtmlOutputTest.php
+++ b/tests/Unit/PendingHtmlOutputTest.php
@@ -5,6 +5,7 @@
 use Phiki\Tests\Fixtures\FakeCache;
 use Phiki\Tests\Fixtures\UselessTransformer;
 use Phiki\Theme\Theme;
+use Phiki\Transformers\Meta;
 
 it('calls transformer methods', function () {
     $transformer = new UselessTransformer;
@@ -104,3 +105,26 @@
 
     expect($pending2->toString())->toBe($pending->toString());
 });
+
+it('passes meta to transformers', function () {
+    $transformer = new class extends UselessTransformer {
+        public function meta(): Meta
+        {
+            return $this->meta;
+        }
+    };
+
+    $output = (new Phiki)
+        ->codeToHtml(
+            <<<'PHP'
+            echo "Hello, world!";
+            PHP,
+            Grammar::Php,
+            Theme::GithubLight,
+        )
+        ->transformer($transformer)
+        ->withMeta($meta = new Meta())
+        ->toString();
+
+    expect($transformer->meta())->toBe($meta);
+});