YVONNE MATTHEWS and GUEST / "Kwanzaa" 

In 2011, Novak Djokovic had just about the best year a male tennis player has ever had, including wins at three of the four Grand Slam tournaments.

"This is the athlete of the year," says Jon Wertheim of Sports Illustrated. "This is a brutal, brutal sport. This guy is playing on six continents, every surface....This is one of the all time great years in open tennis history."

This year, Djokovic also kept to a gluten-free diet. Must have been particularly difficult since his family's business is a pizza parlor.

At rodeos, barrel racing has long been a popular event. Riders, often young women, race their horses in a cloverleaf pattern around barrels in an arena. Using quarter horses, the sport has grown in popularity in recent years and has its own circuit of races and competitive riders.

But in Gretna, Fla., a plan to turn barrel racing into a betting proposition has run into opposition. Quarter horse breeders and trainers are suing to stop it, saying the new event could destroy their industry.

The digital cloud became a household word in 2011.You can now store and share things via the Internet in ways you never could before. But what does the cloud look like, and where can we find it?

The section of the cloud we visited has a lot of concrete and security.

Behind a ballistics-grade door, data center owner David Sabey ushers us into a spotless Seattle-area facility the size of nine football fields. It's crammed full of racks upon racks of powerful servers, sophisticated computers that serve up information. There are lots of blinking lights and wires everywhere.

Hurricanes topple plenty of trees, but when you think about it, the more amazing thing is that many trees can stand up to these 100-mile-per-hour winds.

Now a French scientist has come up with an explanation for the resilience of trees. And astonishingly, the answer was first described by Leonardo da Vinci 500 years ago.

Leonardo noticed that when trees branch, smaller branches have a precise, mathematical relationship to the branch from which they sprang. Many people have verified Leonardo's rule, as it's known, but no one had a good explanation for it.

Harold O'Neal is a jazz pianist with an unusual resume. Born in Tanzania and raised in Kansas City, Miss., O'Neal is also a hip-hop dancer, martial artist and actor. He's just released a new album with an unusual back story of its own: Marvelous Fantasy is a largely improvised collection of solo piano pieces, an homage to the music of silent films.

Earlier this year, Alabama passed a tough immigration law that prompted thousands of migrant workers to flee the state.

Shortly after, NPR spoke with Jamie Boatwright, a fourth-generation tomato farmer in Steele, Ala. When the law was passed, about 20 of Boatwright's farmhands — all of them from Mexico — left and his business was devastated.