When Penny returns from visiting her family in Nebraska, Leonard is happy to see her. Sheldon, however, is much less welcoming when he learns that her family has the flu.

Sigrid begins her tale of how she ended up in Italy, where she's now living. She was born in Minneapolis and raised in New York. As a young adult, she relocated to Switzerland in order to study early music. In this video, she talks about traveling to Europe for the first time and learning about the different genres of music prior to the classical era.

Leonard finally tells Penny how Sheldon saved his life and broke the elevator at the same time.

The President and First Lady kick off an evening of poetry, music, and the spoken word at the White House.

Miss World 2013 Megan Young from the Philippines continues her tour of London!

Rozalia Project knows all about marine debris. Do you? Take a look at their wrap-up video from Expedition CLEAN on the Gulf of Maine in August of 2014.

Mark King of the band Level 42 is a tourism ambassador for the Isle of Wight. Here he explains why.

Real estate magnate, television celebrity and current Republican presidential candidate sat down for an interview with Jimmy Carter. Take a look!

Australian rockers AC/DC perform their classic heavy metal anthem "Highway to Hell" in Argentina to a crowd of sixty thousand fans.

These DIY hatching chick deviled eggs for Easter are the perfect dish to serve this spring, and once you watch this video, you'll learn how easy they are to make. Just be careful, they're so adorable, everyone is going to want one of their own!

Within a deep and narrow cave in South Africa, paleoanthropologist Lee Berger and his team found fossil remains belonging to the newest member of our human family. The Homo naledi discovery adds another exciting chapter to the human evolution story by introducing an ancestor that was primitive, but shared physical characteristics with modern humans.

This is Amie Ann Duffy, the Welsh singer-songwriter known as Duffy, performing her signature song "Mercy" from her debut album Rockferry. It was released in 2008 and achieved worldwide chart success.

Peyton Manning explains why his brother had such a bummed out expression on his face after his Super Bowl 50 win. It turns out that wasn't the first time he's gotten that look from Eli.

In this final installment of the series, a white Kermode bear encounters a black bear while fishing. Observe their behavior. Look and see for yourself what ensues!

Romantic chemistry is all about warm, gooey feelings that gush from the deepest depths of the heart... right? Not quite. Actually, the real boss behind attraction is your brain, which runs through a very quick, very complex series of calculations when assessing a potential partner. Dawn Maslar explores how our five senses contribute to this mating game, citing some pretty wild studies along the way.