diff --git a/README.md b/README.md
index f10fcbd..352eab6 100644
--- a/README.md
+++ b/README.md
@@ -53,29 +53,68 @@ This library includes many rules for a single desired piece of metadata which sh
 This library provides rules to find the following forms of metadata in a page:
 
 Field | Description
---- | --- 
+--- | ---
 type | The type of content as defined by [opengraph](http://ogp.me/#types).
 url | A canonical URL for the page.
 title | A user displayable title for the page.
 description | A user displayable description for the page.
 icon_url | A URL which contains an icon for the page.
 image_url | A URL which contains a preview image for the page.
+keywords | The meta keywords for the page.
 
-To use a single rule to find a particular piece of metadata within a page, simply pass that rule a [Document](https://developer.mozilla.org/en-US/docs/Web/API/Document) object and it will apply each possible selector for that rule until it finds a matching piece of information and return it.
+To use a single rule to find a particular piece of metadata within a page, simply pass that rule  and a [Document](https://developer.mozilla.org/en-US/docs/Web/API/Document) object to getMetadata and it will apply each possible selector for that rule until it finds a matching piece of information and return it.
 
 Example:
 
-    const {metadataRules} = require('page-metadata-parser');
+    const {getMetadata, metadataRules} = require('page-metadata-parser');
 
-    const pageTitle = metadataRules.title(document);
+    const pageTitle = getMetadata(doc, {title: metadataRules.title});
+
+
+### Extending a single rule
+
+To add your own additional custom parser to an existing rule, you can simply push it into that rule's array.
+
+Example:
+
+
+    const {getMetadata, metadataRules} = require('page-metadata-parser');
+
+    const customDescriptionRules = metadataRules.description;
+
+    customDescriptionRules.push([
+      ['meta[name="customDescription"]', node => node.element.content]
+    ]);
+
+    const pageDescription = getMetadata(doc, {description: customDescriptionRules});
 
 
 ### Using all rules
 
 To parse all of the available metadata on a page using all of the rules provided in this library, simply call getMetadata on the [Document](https://developer.mozilla.org/en-US/docs/Web/API/Document).
 
-    const {getMetadata} = require('page-metadata-parser');
+    const {getMetadata, metadataRules} = require('page-metadata-parser');
+
+    const pageMetadata = getMetadata(doc, metadataRules);
+
+
+### Nesting rules
+
+You can nest rules into arbitrarily deep object structures which will mirror the structure of the returned metadata payload.
+
+Example:
+
+    const {getMetadata, metadataRules} = require('page-metadata-parser');
 
-    const pageMetadata = getMetadata(document);
+    const nestedMetadataRules = {
+      images: {
+        preview: metadataRules.image_url,
+        icon: metadataRules.icon_url,
+      },
+      text: {
+        title: metadataRules.title,
+        description: metadataRules.description,
+      }
+    };
 
-    const pageTitle = pageMetadata.title;
+    const nestedMetadata = getMetadata(doc, nestedMetadataRules); 
diff --git a/parser.js b/parser.js
index b1e44af..f1987d0 100644
--- a/parser.js
+++ b/parser.js
@@ -1,6 +1,5 @@
 const {dom, rule, ruleset} = require('fathom-web');
 
-
 function buildRuleset(name, rules) {
   const reversedRules = Array.from(rules).reverse();
   const builtRuleset = ruleset(...reversedRules.map(([query, handler], order) => rule(
@@ -24,77 +23,64 @@ function buildRuleset(name, rules) {
   };
 }
 
-
-const titleRules = buildRuleset('title', [
-  ['meta[property="og:title"]', node => node.element.content],
-  ['meta[property="twitter:title"]', node => node.element.content],
-  ['meta[name="hdl"]', node => node.element.content],
-  ['title', node => node.element.text],
-]);
-
-const canonicalUrlRules = buildRuleset('url', [
-  ['meta[property="og:url"]', node => node.element.content],
-  ['link[rel="canonical"]', node => node.element.href],
-]);
-
-const keywordsRules = buildRuleset('keywords', [
-  ['meta[name="keywords"]', node => node.element.content],
-]);
-
-const iconRules = buildRuleset('icon', [
-  ['link[rel="apple-touch-icon"]', node => node.element.href],
-  ['link[rel="apple-touch-icon-precomposed"]', node => node.element.href],
-  ['link[rel="icon"]', node => node.element.href],
-  ['link[rel="fluid-icon"]', node => node.element.href],
-  ['link[rel="shortcut icon"]', node => node.element.href],
-  ['link[rel="Shortcut Icon"]', node => node.element.href],
-  ['link[rel="mask-icon"]', node => node.element.href],
-]);
-
-const imageRules = buildRuleset('image', [
-  ['meta[property="og:image:secure_url"]', node => node.element.content],
-  ['meta[property="og:image:url"]', node => node.element.content],
-  ['meta[property="og:image"]', node => node.element.content],
-  ['meta[property="twitter:image"]', node => node.element.content],
-  ['meta[name="thumbnail"]', node => node.element.content],
-]);
-
-const descriptionRules = buildRuleset('description', [
-  ['meta[property="og:description"]', node => node.element.content],
-  ['meta[name="description"]', node => node.element.content],
-]);
-
-const typeRules = buildRuleset('type', [
-  ['meta[property="og:type"]', node => node.element.content],
-]);
-
-
 const metadataRules = {
-  description: descriptionRules,
-  icon_url: iconRules,
-  image_url: imageRules,
-  keywords: keywordsRules,
-  title: titleRules,
-  type: typeRules,
-  url: canonicalUrlRules
+  description: [
+    ['meta[property="og:description"]', node => node.element.content],
+    ['meta[name="description"]', node => node.element.content],
+  ],
+  icon_url: [
+    ['link[rel="apple-touch-icon"]', node => node.element.href],
+    ['link[rel="apple-touch-icon-precomposed"]', node => node.element.href],
+    ['link[rel="icon"]', node => node.element.href],
+    ['link[rel="fluid-icon"]', node => node.element.href],
+    ['link[rel="shortcut icon"]', node => node.element.href],
+    ['link[rel="Shortcut Icon"]', node => node.element.href],
+    ['link[rel="mask-icon"]', node => node.element.href],
+  ],
+  image_url: [
+    ['meta[property="og:image:secure_url"]', node => node.element.content],
+    ['meta[property="og:image:url"]', node => node.element.content],
+    ['meta[property="og:image"]', node => node.element.content],
+    ['meta[property="twitter:image"]', node => node.element.content],
+    ['meta[name="thumbnail"]', node => node.element.content],
+  ],
+  keywords: [
+    ['meta[name="keywords"]', node => node.element.content],
+  ],
+  title: [
+    ['meta[property="og:title"]', node => node.element.content],
+    ['meta[property="twitter:title"]', node => node.element.content],
+    ['meta[name="hdl"]', node => node.element.content],
+    ['title', node => node.element.text],
+  ],
+  type: [
+    ['meta[property="og:type"]', node => node.element.content],
+  ],
+  url: [
+    ['meta[property="og:url"]', node => node.element.content],
+    ['link[rel="canonical"]', node => node.element.href],
+  ],
 };
 
-
 function getMetadata(doc, rules) {
   const metadata = {};
   const ruleSet = rules || metadataRules;
 
   Object.keys(ruleSet).map(metadataKey => {
     const metadataRule = ruleSet[metadataKey];
-    metadata[metadataKey] = typeof metadataRule === 'function' ?
-      metadataRule(doc) :
-      getMetadata(doc, metadataRule);
+
+    if(Array.isArray(metadataRule)) {
+      metadata[metadataKey] = buildRuleset(metadataKey, metadataRule)(doc);
+    } else {
+      metadata[metadataKey] = getMetadata(doc, metadataRule);
+    }
   });
 
   return metadata;
 }
 
 module.exports = {
+  buildRuleset,
   metadataRules,
   getMetadata
 };
diff --git a/tests/metadataRules.test.js b/tests/metadataRules.test.js
index fcaf0c1..6488209 100644
--- a/tests/metadataRules.test.js
+++ b/tests/metadataRules.test.js
@@ -1,6 +1,6 @@
 // Tests for parse.js
 const {assert} = require('chai');
-const {metadataRules} = require('../parser');
+const {buildRuleset, metadataRules} = require('../parser');
 const {stringToDom} = require('./test-utils');
 
 function buildHTML(tag) {
@@ -17,7 +17,8 @@ function ruleTest(testName, testRule, expected, testTag) {
   it(`finds ${testName}`, () => {
     const html = buildHTML(testTag);
     const doc = stringToDom(html);
-    const found = testRule(doc);
+    const rule = buildRuleset(testName, testRule);
+    const found = rule(doc);
     assert.equal(found, expected, `Unable to find ${testName} in ${html}`);
   });
 }