Partially collapsing posts

I’m just wondering if anyone does how I could collapse the posts I put up in order to save on room as they are generally quite long. I want only the first few paragraphs to show and the rest to be accesible with a click that drops the rest of the text in the article. I’ve seen it done on a few sites before so I know its possible. I’ve checked the plugin section but the one for collapsing posts seems to be the only one that isnt available. This is the site, http://www.friedrichzenkner.com. Thanks in advance.