
Mensa-fied best friends and roommates Leonard and Sheldon, physicists who work at the California Institute of Technology, may be able to tell everybody more than they want to know about quantum physics, but getting through most basic social situations, especially ones involving women, totally baffles them. How lucky, then, that babe-alicious waitress/aspiring actress Penny moves in next door. Frequently seen hanging out with Leonard and Sheldon are friends and fellow Caltech scientists Wolowitz and Koothrappali. Will worlds collide? Does Einstein theorize in the woods?

Leonard must choose who to bring with him when he goes to see the Large Hadron Collider on Valentine's Day.

Leonard, realizing his pursuit of Penny is fruitless, has an unexpected encounter with a fellow scientist (Sara Gilbert).

Sheldon pushes himself to the limit when he collaborates on projects with Leonard and Wolowitz as well as Amy on the same day; Bernadette nears the end of her maternity leave and must return to work.

Leonard, Penny and Raj settle into their new living arrangement; Sheldon expresses interest in Amy's work.