Cat Or Dog? Sure, you can easily tell the difference. But a machine may not be able to guess on the first try. iStockphoto hide caption

itoggle caption iStockphoto

New research finds a close connection between the flu that devastated the horse population in North America in the 1870s and the avian flu of that period. Hulton Archive/Getty Images hide caption

itoggle caption Hulton Archive/Getty Images

The brain edits memories of the past, updating them with new information. Scientists say this may help us function better in the present. But don't throw those photos away. iStockphoto hide caption

itoggle caption iStockphoto

A mouse embryo grows from stem cells made by stressing blood cells with acid. The blood cells are tagged with a protein that creates green light. Courtesy of Haruko Obokata hide caption

itoggle caption Courtesy of Haruko Obokata

The sexually transmitted cancer is common in street dogs around the world. Noel Celis/AFP/Getty Images hide caption

itoggle caption Noel Celis/AFP/Getty Images

The superglue developed by scientists sticks to wet, bloody surfaces. Researchers hope the adhesive could one day seal a torn vessels or fix heart defects. Randal McKenzie / McKenzie Illustrations. hide caption

itoggle caption Randal McKenzie / McKenzie Illustrations.

There's data to support the notion that pot, or a drug based on its active ingredient, could help ease the fears of PTSD. Ted S. Warren/AP hide caption

itoggle caption Ted S. Warren/AP

Research excavations like these in Siberia's Denisova Cave are yielding clues to the mating choices of early hominids. Bence Viola/Nature hide caption

itoggle caption Bence Viola/Nature

Yes, you could do this at home. Growing bacteria you find in a pile of dirt or a local pond might reveal the next big antibiotic. Charlotte Raymond/Science Source hide caption

itoggle caption Charlotte Raymond/Science Source

President Obama walks into an auditorium in the Eisenhower Executive Office Building Monday for a speech about World AIDS Day. Carolyn Kaster/AP hide caption

itoggle caption Carolyn Kaster/AP

Lefties don't necessarily do everything with their left hand, and the ones who do might not use the right side of their brain for language. iStockphoto hide caption

itoggle caption iStockphoto

University of California, Davis food safety field scientists Michele Jay-Russell, Paula Kahn-Rivadeneira, Anna Zwieniecka, Navreen Pandher and Peiman Aminabadi celebrate the first day of their experiment testing E. coli survival in soil. Courtesy of Fhon Saharuetai hide caption

itoggle caption Courtesy of Fhon Saharuetai