Some 66 million years ago, about 75 percent of species on Earth disappeared. It wasn't just dinosaurs but most large mammals, fish, birds and plankton. Scientists have known this for a long time just from looking at the fossil record. If you dig deep enough, you find lots of dinosaur bones. And then a few layers up, they're gone.
But scientists couldn't figure out exactly what had caused this phenomenon. Of course, there were lots of theories.
The faces of American Kim Lee and her Chinese husband, Li Yang, both in their 40s, once graced the covers of books that sold in the millions. He was China's most famous English teacher, the "Crazy English" guru of China, who pioneered his own style of English teaching: pedagogy through shouted language, yelling to halls of thousands of students.
His methods were given official recognition after he was employed by the Beijing Olympic Organizing Committee to teach Olympic volunteers.
Just a stone's throw from two of Los Angeles' busiest freeways lies the Sepulveda Basin Wildlife Reserve, a unique spot in an urban jungle.
The northern portion of the reserve is adorned with 30-foot-tall cottonwood trees, spots of coyote bush and other plants. Native plants cover 50 percent of the nature spot, says Kris Ohlenkamp with the San Fernando Valley Audubon Society.
"On the other side it was significantly more than that," he says.
Minnesota has a Democratic governor, two Democratic senators, and Democrats control both houses of its Legislature. So it may have come as no surprise when President Obama went there earlier this week to rally support for his proposals to reduce gun violence.
But even in the politically blue state, there's considerable resistance to placing further restrictions on gun ownership.
During his visit to a Minneapolis police facility Monday, Obama urged Minnesotans to find common ground in curbing gun violence.