diff --git a/src/StackFormation/PreProcessor/Stage/AbstractTreePreProcessorStage.php b/src/StackFormation/PreProcessor/Stage/AbstractTreePreProcessorStage.php
index 8d38f76..b68fb9a 100644
--- a/src/StackFormation/PreProcessor/Stage/AbstractTreePreProcessorStage.php
+++ b/src/StackFormation/PreProcessor/Stage/AbstractTreePreProcessorStage.php
@@ -7,30 +7,33 @@
 abstract class AbstractTreePreProcessorStage
 {
     protected $treePreProcessor; // reference to parent
+    protected $template;
 
     /**
      * @param \StackFormation\PreProcessor\TreePreProcessor $treePreProcessor
+     * @param Template $template
      */
-    public function __construct(\StackFormation\PreProcessor\TreePreProcessor $treePreProcessor) {
+    public function __construct(\StackFormation\PreProcessor\TreePreProcessor $treePreProcessor, Template $template) {
         $this->treePreProcessor = $treePreProcessor;
+        $this->template = $template;
     }
 
     /**
-     * @param Template $template
-     * @return Template $template
      * @throws \StackFormation\Exception\TreePreProcessorException
      */
-    public function __invoke(Template $template)
+    public function __invoke()
     {
         try {
-            return $this->invoke($template);
+            $tree = $this->template->getTree();
+            $this->invoke($tree);
+            $this->template->setTree($tree);
         } catch (\Exception $e) {
-            throw new \StackFormation\Exception\TreePreProcessorException($template, $e);
+            throw new \StackFormation\Exception\TreePreProcessorException($this->template, $e);
         }
     }
 
     /**
-     * @param Template $template
+     * @param $tree
      */
-    abstract function invoke(Template $template);
+    abstract function invoke(array &$tree);
 }
diff --git a/src/StackFormation/PreProcessor/Stage/Tree/ExpandPort.php b/src/StackFormation/PreProcessor/Stage/Tree/ExpandPort.php
index 8b66ff4..b733f3f 100644
--- a/src/StackFormation/PreProcessor/Stage/Tree/ExpandPort.php
+++ b/src/StackFormation/PreProcessor/Stage/Tree/ExpandPort.php
@@ -3,24 +3,18 @@
 namespace StackFormation\PreProcessor\Stage\Tree;
 
 use StackFormation\PreProcessor\Stage\AbstractTreePreProcessorStage;
-use StackFormation\Template;
 
 class ExpandPort extends AbstractTreePreProcessorStage
 {
     /**
-     * @param Template $template
-     * @return Template $template
+     * @param array $tree
      */
-    public function invoke(Template $template)
+    public function invoke(array &$tree)
     {
-        $tree = $template->getTree();
-        $this->treePreProcessor->searchTreeByExpression('/^Port$/', $tree, function (&$tree, $key, $value) {
+        $this->treePreProcessor->searchTreeByExpression('/^Port$/', $tree, function (&$tree, $key, $value, $matches) {
             unset($tree[$key]);
             $tree['FromPort'] = $value;
             $tree['ToPort'] = $value;
-        }, 'key');
-        $template->setTree($tree);
-
-        return $template;
+        }, true);
     }
 }
diff --git a/src/StackFormation/PreProcessor/Stage/Tree/InjectFilecontent.php b/src/StackFormation/PreProcessor/Stage/Tree/InjectFilecontent.php
new file mode 100644
index 0000000..466b346
--- /dev/null
+++ b/src/StackFormation/PreProcessor/Stage/Tree/InjectFilecontent.php
@@ -0,0 +1,86 @@
+<?php
+
+namespace StackFormation\PreProcessor\Stage\Tree;
+
+use StackFormation\PreProcessor\Stage\AbstractTreePreProcessorStage;
+use Symfony\Component\Filesystem\Exception\FileNotFoundException;
+
+class InjectFilecontent extends AbstractTreePreProcessorStage
+{
+    const MAX_JS_FILE_INCLUDE_SIZE = 4096;
+
+    /**
+     * @param array $tree
+     */
+    public function invoke(array &$tree)
+    {
+        // Search in array key
+        $this->treePreProcessor->searchTreeByExpression('/^Fn::FileContent(|Unpretty|TrimLines|Minify)$/', $tree, function (array &$tree, $key, $value, $matches) {
+            unset($tree[$key]);
+            $lines = $this->renderFileContent($value, $matches[1]);
+            $tree['Fn::Join'] = [ '', [implode('', $lines)]];
+        }, true);
+
+        // Search in values (content)
+        $this->treePreProcessor->searchTreeByExpression('/Fn::FileContent(|Unpretty|TrimLines|Minify)(:)(.*)/', $tree, function (array &$tree, $key, $value, $matches) {
+            unset($tree[$key]);
+            $lines = $this->renderFileContent(trim(end($matches)), $matches[1]);
+            $tree[$key] = ['Fn::Join' => [ '', [implode('', $lines)]]];
+        });
+    }
+
+    /**
+     * @param string $file
+     * @param string $modus
+     * @return array
+     * @throws \Exception
+     */
+    protected function renderFileContent($file, $modus)
+    {
+        $file = $this->template->getBasePath() . '/' . $file;
+        if (!is_file($file)) {
+            throw new FileNotFoundException("File '$file' not found");
+        }
+
+        $ext = pathinfo($file, PATHINFO_EXTENSION);
+        if ($modus == 'Minify' && $ext != 'js') {
+            throw new \Exception('Fn::FileContentMinify is only supported for *.js files. (File: ' . $file . ')');
+        }
+
+        $fileContent = file_get_contents($file);
+
+        # TODO in own stage ?
+        #$fileContent = $this->injectInclude($fileContent, dirname(realpath($file)));
+
+        if ($ext === 'js') {
+            if ($modus == 'Minify') {
+                $fileContent = \JShrink\Minifier::minify($fileContent, ['flaggedComments' => false]);
+            }
+
+            $size = strlen($fileContent);
+            if ($size > self::MAX_JS_FILE_INCLUDE_SIZE) {
+                // this is assuming you are uploading an inline JS file to AWS Lambda
+                throw new \Exception(sprintf("JS file is larger than %s bytes (actual size: %s bytes)", self::MAX_JS_FILE_INCLUDE_SIZE, $size));
+            }
+        }
+
+        // TODO: this isn't optimal. Why are we processing this here in between?
+        #$fileContent = $this->base64encodedJson($fileContent);
+
+        $lines = explode("\n", $fileContent);
+        foreach ($lines as $lineKey => &$line) {
+            if ($modus == 'TrimLines') {
+                $line = trim($line);
+                if (empty($line)) {
+                    unset($lines[$lineKey]);
+                }
+            }
+            $line .= "\n";
+        }
+
+        #$whitespace = trim($matches[1], "\n");
+        #$result = str_replace("\n", "\n" . $whitespace, $result);
+
+        return $lines;
+    }
+}
diff --git a/src/StackFormation/PreProcessor/TreePreProcessor.php b/src/StackFormation/PreProcessor/TreePreProcessor.php
index ded63ab..2e7425c 100644
--- a/src/StackFormation/PreProcessor/TreePreProcessor.php
+++ b/src/StackFormation/PreProcessor/TreePreProcessor.php
@@ -15,10 +15,10 @@ public function process(Template $template)
     {
         $stageClasses = [
             '\StackFormation\PreProcessor\Stage\Tree\ExpandPort',
+            '\StackFormation\PreProcessor\Stage\Tree\InjectFilecontent',
 
             # TODO, check also if we still need that
             #'\StackFormation\PreProcessor\Stage\Tree\ParseRefInDoubleQuotedStrings',
-            #'\StackFormation\PreProcessor\Stage\Tree\InjectFilecontent',
             #'\StackFormation\PreProcessor\Stage\Tree\Base64encodedJson',
             #'\StackFormation\PreProcessor\Stage\Tree\Split',
             #'\StackFormation\PreProcessor\Stage\Tree\ReplaceFnGetAttr',
@@ -28,30 +28,32 @@ public function process(Template $template)
 
         $pipeline = new Pipeline();
         foreach ($stageClasses as $stageClass) {
-            $pipeline->addStage(new $stageClass($this));
+            $pipeline->addStage(new $stageClass($this, $template));
         }
 
-        return $pipeline->process($template);
+        $pipeline->process('');
     }
 
     /**
      * @param string $expression
      * @param array $tree
      * @param callable $callback
-     * @param string $mode
+     * @param bool $expressionUsedOnKey
      */
-    public function searchTreeByExpression($expression, array &$tree, callable $callback, $mode = '')
+    public function searchTreeByExpression($expression, array &$tree, callable $callback, $expressionUsedOnKey = false)
     {
+        #print_r($tree);die();
+
         foreach ($tree as $key => &$leaf) {
             if (is_array($leaf)) {
-                $this->searchTreeByExpression($expression, $leaf, $callback, $mode);
+                $this->searchTreeByExpression($expression, $leaf, $callback, $expressionUsedOnKey);
                 continue;
             }
 
-            $subject = ($mode == 'key' ? $key : $leaf);
-            if (preg_match($expression, $subject)) {
-                $callback($tree, $key, $leaf);
-            }
+            $subject = ($expressionUsedOnKey === true ? $key : $leaf);
+            preg_replace_callback($expression, function(array $matches) use ($callback, &$tree, $key, $leaf) {
+                $callback($tree, $key, $leaf, $matches);
+            }, $subject);
         }
     }
 }
diff --git a/src/StackFormation/PrefixedTemplate.php b/src/StackFormation/PrefixedTemplate.php
index ebb14e9..3a83896 100644
--- a/src/StackFormation/PrefixedTemplate.php
+++ b/src/StackFormation/PrefixedTemplate.php
@@ -37,6 +37,13 @@ public function getProcessedTemplate()
         if ($this->prefix) {
             if (!$this->cache->has(__METHOD__)) {
                 $content = parent::getProcessedTemplate();
+
+
+
+
+                # TODO $content is now an Template object
+
+
                 $content = $this->updateRef($this->prefix, $content);
                 $content = $this->updateDependsOn($this->prefix, $content);
                 $content = $this->updateDependsOnMultiple($this->prefix, $content);
@@ -47,6 +54,14 @@ public function getProcessedTemplate()
 
             return $this->cache->get(__METHOD__);
         } else {
+
+
+
+
+            # TODO return $this instead of
+
+
+
             return parent::getProcessedTemplate();
         }
     }
diff --git a/src/StackFormation/Template.php b/src/StackFormation/Template.php
index b96540f..e143b65 100644
--- a/src/StackFormation/Template.php
+++ b/src/StackFormation/Template.php
@@ -60,7 +60,8 @@ public function getProcessedTemplate()
         return $this->cache->get(
             __METHOD__,
             function () {
-                return $this->treePreProcessor->process($this);
+                $this->treePreProcessor->process($this);
+                return $this;
             }
         );
     }
@@ -78,16 +79,16 @@ public function getData()
             $yamlParser = new \Symfony\Component\Yaml\Parser();
             $this->tree = $yamlParser->parse($fileContent);
 
-            $this->getProcessedTemplate();
+            $template = $this->getProcessedTemplate();
 
-            if (!is_array($this->tree)) {
-                throw new TemplateDecodeException($this->getFilePath(), sprintf("Error decoding file '%s'", $this->getFilePath()));
+            if (!is_array($template->getTree())) {
+                throw new TemplateDecodeException($template->getFilePath(), sprintf("Error decoding file '%s'", $template->getFilePath()));
             }
-            if ($this->tree['AWSTemplateFormatVersion'] != '2010-09-09') {
-                throw new TemplateInvalidException($this->getFilePath(), 'Invalid AWSTemplateFormatVersion');
+            if ($template->tree['AWSTemplateFormatVersion'] != '2010-09-09') {
+                throw new TemplateInvalidException($template->getFilePath(), 'Invalid AWSTemplateFormatVersion');
             }
 
-            $this->cache->set(__METHOD__, $this->tree);
+            $this->cache->set(__METHOD__, $template->tree);
         }
 
         return $this->cache->get(__METHOD__);
diff --git a/src/StackFormation/TemplateMerger.php b/src/StackFormation/TemplateMerger.php
index d66ff0d..ff6cb8d 100644
--- a/src/StackFormation/TemplateMerger.php
+++ b/src/StackFormation/TemplateMerger.php
@@ -64,8 +64,7 @@ public function merge(array $templates, $description = null, array $additionalDa
                 if (Div::isProgramInstalled('jq')) {
                     $tmpfile = tempnam(sys_get_temp_dir(), 'json_validate_');
                     $yaml = new \Symfony\Component\Yaml\Yaml();
-                    $output = $yaml->dump($template->getProcessedTemplate());
-                    file_put_contents($tmpfile, $output);
+                    file_put_contents($tmpfile, $yaml->dump($data));
                     passthru('jq . ' . $tmpfile);
                     unlink($tmpfile);
                 }
diff --git a/tests/StackFormation/PreprocessorTest.php b/tests/StackFormation/PreprocessorTest.php
index 010a50e..3d179b5 100644
--- a/tests/StackFormation/PreprocessorTest.php
+++ b/tests/StackFormation/PreprocessorTest.php
@@ -12,6 +12,19 @@ class PreprocessorTest extends \PHPUnit_Framework_TestCase
     public function setUp()
     {
         parent::setUp();
+
+
+
+        #
+        #
+        # TODO switch Preprocessor and rewrite/add tests
+        #
+        #
+        #
+        #
+
+
+
         $this->preprocessor = new \StackFormation\Preprocessor();
     }