diff --git a/src/Extension/Form.php b/src/Extension/Form.php
new file mode 100644
index 0000000..7997d05
--- /dev/null
+++ b/src/Extension/Form.php
@@ -0,0 +1,158 @@
+<?php
+
+namespace Mapped\Extension;
+
+use Mapped\Mapping;
+use Mapped\ValidationException;
+
+/**
+ * Form.
+ */
+class Form implements \ArrayAccess
+{
+    private $mapping;
+    private $children = [];
+    private $value;
+    private $data;
+    private $errors = [];
+
+    /**
+     * Constructor.
+     *
+     * @param Mapping $mapping  The mapping object
+     * @param Form[]  $children An array of form objects
+     */
+    public function __construct(Mapping $mapping, array $children = [])
+    {
+        $this->mapping = $mapping;
+        $this->children = $children;
+    }
+
+    /**
+     * Binds the given data to the form.
+     *
+     * @param mixed $data The submitted data
+     */
+    public function bind($data)
+    {
+        try {
+            $this->data = $this->mapping->apply($data);
+        } catch (ValidationException $e) {
+            $this->errors = $e->getErrors();
+        }
+    }
+
+    /**
+     * Fills the form.
+     *
+     * @param mixed $data The data
+     */
+    public function fill($data)
+    {
+        $this->value = $this->mapping->unapply($data);
+    }
+
+    /**
+     * Returns true if this form is valid, otherwise false.
+     *
+     * @return bool
+     */
+    public function isValid()
+    {
+        return 0 === count($this->errors);
+    }
+
+    /**
+     * Sets data.
+     *
+     * @param mixed $data Some data
+     */
+    public function setData($data)
+    {
+        $this->data = $data;
+    }
+
+    /**
+     * Gets the data (the applied result).
+     *
+     * return mixed
+     */
+    public function getData()
+    {
+        return $this->data;
+    }
+
+    /**
+     * Sets value.
+     *
+     * @param mixed $value Some value
+     */
+    public function setValue($value)
+    {
+        $this->value = $value;
+    }
+
+    /**
+     * Gets the value (The unapplied result).
+     *
+     * @return mixed
+     */
+    public function getValue()
+    {
+        return $this->value;
+    }
+
+    /**
+     * Sets errors.
+     *
+     * @param Error[] $errors An array of error objects
+     */
+    public function setErrors(array $errors)
+    {
+        $this->errors = $errors;
+    }
+
+    /**
+     * Gets the errors.
+     *
+     * @return Error[]
+     */
+    public function getErrors()
+    {
+        return $this->errors;
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function offsetGet($offset)
+    {
+        if ($this->offsetExists($offset)) {
+            return $this->children[$offset];
+        }
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function offsetExists($offset)
+    {
+        return isset($this->children[$offset]);
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function offsetSet($offset, $value)
+    {
+        throw new \RuntimeException('Not implemented');
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function offsetUnset($offset)
+    {
+        throw new \RuntimeException('Not implemented');
+    }
+}
diff --git a/src/Extension/Forms.php b/src/Extension/Forms.php
new file mode 100644
index 0000000..f664294
--- /dev/null
+++ b/src/Extension/Forms.php
@@ -0,0 +1,42 @@
+<?php
+
+namespace Mapped\Extension;
+
+use Mapped\ExtensionInterface;
+use Mapped\Mapping;
+use Mapped\Events;
+
+/**
+ * Forms.
+ */
+class Forms implements ExtensionInterface
+{
+    /**
+     * Returns a form.
+     *
+     * @param Mapping $mapping The mapping object
+     *
+     * @return Form
+     */
+    public function form(Mapping $mapping)
+    {
+        $children = array_map(function (Mapping $child) {
+            return $child->form();
+        }, $mapping->getChildren());
+
+        $form = new Form($mapping, $children);
+        $emitter = $mapping->getEmitter();
+
+        $emitter->on(Events::APPLIED, function ($data) use ($form) {
+            $form->setData($data->getResult());
+            $form->setValue($data->getInput());
+            $form->setErrors($data->getErrors());
+        });
+        
+        $emitter->on(Events::UNAPPLIED, function ($data) use ($form) {
+            $form->setValue($data->getResult());
+        });
+
+        return $form;
+    }
+}
diff --git a/tests/Extension/FormTest.php b/tests/Extension/FormTest.php
new file mode 100644
index 0000000..718f17b
--- /dev/null
+++ b/tests/Extension/FormTest.php
@@ -0,0 +1,47 @@
+<?php
+
+namespace Mapped\Tests\Extension;
+
+use Mapped\Extension\Form;
+
+class FormTest extends \PHPUnit_Framework_TestCase
+{
+    public function testOffsetGetAndExists()
+    {
+        $mapping = $this->getMockBuilder('Mapped\Mapping')
+            ->disableOriginalConstructor()
+            ->getMock();
+
+        $form = new Form($mapping, [
+            'foo' => new Form($mapping),
+            'bar' => new Form($mapping),
+        ]);
+
+        $this->assertNotNull($form['foo']);
+        $this->assertNull($form['baz']);
+        $this->assertTrue(isset($form['foo']));
+        $this->assertFalse(isset($form['baz']));
+    }
+
+    public function testOffsetSet()
+    {
+        $this->setExpectedException('RuntimeException');
+        $mapping = $this->getMockBuilder('Mapped\Mapping')
+            ->disableOriginalConstructor()
+            ->getMock();
+
+        $form = new Form($mapping);
+        $form['foo'] = $form;
+    }
+
+    public function testOffsetUnset()
+    {
+        $this->setExpectedException('RuntimeException');
+        $mapping = $this->getMockBuilder('Mapped\Mapping')
+            ->disableOriginalConstructor()
+            ->getMock();
+
+        $form = new Form($mapping);
+        unset($form['foo']);
+    }
+}
diff --git a/tests/Extension/FormsTest.php b/tests/Extension/FormsTest.php
new file mode 100644
index 0000000..f5f6cc8
--- /dev/null
+++ b/tests/Extension/FormsTest.php
@@ -0,0 +1,67 @@
+<?php
+
+namespace Mapped\Tests\Extension;
+
+use Mapped\Factory;
+use Mapped\Tests\Fixtures\User;
+
+class FormsTest extends \PHPUnit_Framework_TestCase
+{
+    public function testA()
+    {
+        $factory = new Factory([new \Mapped\Extension\Forms]);
+        $mapping = $factory->mapping([
+            'username' => $factory->mapping(),
+            'password' => $factory->mapping(),
+        ], function ($username, $password) {
+            return new User($username, $password);
+        }, function (User $user) {
+            return [
+                'username' => $user->username,
+                'password' => $user->password,
+            ];
+        });
+
+        $form = $mapping->form();
+        $form->bind([
+            'username' => 'dennis',
+            'password' => 'passwd',
+        ]);
+
+        $this->assertTrue($form->isValid());
+        $this->assertInstanceOf('Mapped\Tests\Fixtures\User', $form->getData());
+        $this->assertSame('dennis', $form['username']->getData());
+        $this->assertSame('passwd', $form['password']->getData());
+
+        $form->fill($form->getData());
+
+        $this->assertSame([
+            'username' => 'dennis',
+            'password' => 'passwd',
+        ], $form->getValue());
+
+        $this->assertSame('dennis', $form['username']->getValue());
+        $this->assertSame('passwd', $form['password']->getValue());
+    }
+    
+    public function testB()
+    {
+        $factory = new Factory([new \Mapped\Extension\Forms]);
+        $mapping = $factory->mapping([
+            'username' => $factory->mapping()->notEmpty(),
+            'password' => $factory->mapping(),
+        ], function ($username, $password) {
+            return new User($username, $password);
+        });
+
+        $form = $mapping->form();
+        $form->bind(['username' => '']);
+
+        $this->assertFalse($form->isValid());
+        $this->assertCount(2, $form->getErrors());
+        $this->assertCount(1, $form['username']->getErrors());
+        $this->assertCount(1, $form['password']->getErrors());
+        $this->assertSame('error.not_empty', $form['username']->getErrors()[0]->getMessage());
+        $this->assertSame('error.required', $form['password']->getErrors()[0]->getMessage());
+    }
+}