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+In order to use the Assetic OOP API you must first understand the two central
+concepts of Assetic: assets and filters.
+
+### What is an Asset?
+
+As asset is an object that has content and metadata which can be loaded and
+dumped. Your assets will probably fall into three categories: Javascripts,
+stylesheets and images. Most assets will be loaded from files in your
+filesystem, but they can also be loaded via HTTP, a database, from a string,
+or virtually anything else. All that an asset has to do is fulfill Assetic's
+basic asset interface.
+
+### What is a Filter?
+
+A filter is an object that acts upon an asset's content when that asset is
+loaded and/or dumped. Similar to assets, a filter can do virtually anything,
+as long as it implements Assetic's filter interface. 
+
+Here is a list of some of the tools that can be applied to assets using a
+filter:
+
+ * CoffeeScript
+ * CssEmbed
+ * CssMin
+ * Google Closure Compiler
+ * jpegoptim
+ * jpegtran
+ * Less
+ * LessPHP
+ * optipng
+ * Packager
+ * pngout
+ * SASS
+ * Sprockets (version 1)
+ * Stylus
+ * YUI Compressor
+
+### Using Assets and Filters
+
+You need to start by creating an asset object. This will probably mean
+instantiating a `FileAsset` instance, which takes a filesystem path as its
+first argument:
+
+    $asset = new Assetic\Asset\FileAsset('/path/to/main.css');
+
+Once you have an asset you can begin adding filters to it by calling
+`ensureFilter()`. For example, you can add a filter that applies the YUI
+Compressor to the contents of the asset:
+
+    $yui = new Assetic\Filter\Yui\CssCompressorFilter('/path/to/yui.jar');
+    $asset->ensureFilter($yui);
+
+Once you've added as many filters as you'd like you can output the finished
+asset to the browser:
+
+    header('Content-Type: text/css');
+    echo $asset->dump();
+
+### Asset Collections
+
+It is a good idea to combine assets of the same type into a single file to
+avoid unnecessary HTTP requests. You can do this in Assetic using the
+`AssetCollection` class. This class is just like any other asset in Assetic's
+eyes as it implements the asset interface, but under the hood it allows you to
+combine multiple assets into one.
+
+    use Assetic\Asset\AssetCollection;
+
+    $asset = new AssetCollection(array(
+        new FileAsset('/path/to/js/jquery.js'),
+        new FileAsset('/path/to/js/jquery.plugin.js'),
+        new FileAsset('/path/to/js/application.js'),
+    ));
+
+### Nested Asset Collections
+
+The collection class implements the asset interface and all assets passed into
+a collection must implement the same interface, which means you can easily
+nest collections within one another:
+
+    use Assetic\Asset\AssetCollection;
+    use Assetic\Asset\GlobAsset;
+    use Assetic\Asset\HttpAsset;
+
+    $asset = new AssetCollection(array(
+        new HttpAsset('http://example.com/jquery.min.js'),
+        new GlobAsset('/path/to/js/*'),
+    ));
+
+The `HttpAsset` class is a special asset class that loads a file over HTTP;
+`GlobAsset` is a special asset collection class that loads files based on a
+filesystem glob -- both implement the asset interface.
+
+This concept of nesting asset collection become even more powerful when you
+start applying different sets of filters to each collection. Imagine some of
+your application's stylesheets are written in SASS, while some are written in
+vanilla CSS. You can combine all of these into one seamless CSS asset:
+
+    use Assetic\Asset\AssetCollection;
+    use Assetic\Asset\GlobAsset;
+    use Assetic\Filter\SassFilter;
+    use Assetic\Filter\Yui\CssCompressorFilter;
+
+    $css = new AssetCollection(array(
+        new GlobAsset('/path/to/sass/*.sass', array(new SassFilter())),
+        new GlobAsset('/path/to/css/*.css'),
+    ), array(
+        new YuiCompressorFilter('/path/to/yuicompressor.jar'),
+    ));
+
+You'll notice I've also applied the YUI compressor filter to the combined
+asset so all CSS will be minified.
+
+### Iterating over an Asset Collection
+
+Once you have an asset collection you can iterate over it like you would a
+plain old PHP array:
+
+    echo "Source paths:\n";
+    foreach ($collection as $asset) {
+        echo ' - '.$asset->getSourcePath()."\n";
+    }
+
+The asset collection iterates recursively, which means you will only see the
+"leaf" assets during iteration. Iteration also includes a smart filter which
+ensures you only see each asset once, even if the same asset has been included
+multiple times.
+
+Next: [Defining Assets "On The Fly"](define.md)