Leonard and Sheldon are geniuses in the laboratory, but socially challenged in the real world. Enter beautiful, street-smart Penny who aims to teach them a thing or two about life. Leonard believes he's found true love with and Penny and even Sheldon has entered into a "Relationship Agreement" with neurobiologist Amy. In their free time, Leonard and Sheldon enjoy spending time with their expanding universe of friends, Raj and Howard, and Howard's adorable microbiologist wife, Bernadette.