Revealing and Collapsing News

Hello,

I am making a custom theme for a client, who wants to have a news section in a left sidebar. He also want to have the following functionality: When you click a Read more link on any news, it should expand down to reveal the whole content. Then you must have the ability to collapse the news with a read less button/link. Please, could anyone tell me how to code that. Thank you in advance!

Vladimir