A mural in an ancient tomb in China shows a troupe of eunuchs. How long did they live? Wikimedia Commons hide caption

itoggle caption Wikimedia Commons

Federally funded chimps at the New Iberia Research Center in Louisiana will retire to either a lab in Texas or a chimp sanctuary in Louisiana. Courtesy of the Humane Society of the United States hide caption

itoggle caption Courtesy of the Humane Society of the United States

The genetic factors responsible for a cat's stripes might help researchers understand disease resistance in humans. kennymatic via Flickr hide caption

itoggle caption kennymatic via Flickr

Human chromosomes like these contain genes and lots of other genetic material whose function has been a mystery. National Cancer Institute via AP hide caption

itoggle caption National Cancer Institute via AP

Childhood obesity is on the rise in many countries and overuse of antibiotics is now on the radar as a possible factor in the epidemic. Here 18-month-old twins are weighed in a nutritionist's office in Colombia. Raul Arboleda/AFP/Getty Images hide caption

itoggle caption Raul Arboleda/AFP/Getty Images

The white arrows in these two tumor samples point to a subset of tumor cells that are in a resting state. Nature hide caption

itoggle caption Nature

Can You Help Me Tie My Shoe? Researchers found that when study participants were asked an unusual request, they were more likely later on to perform a favor. iStockphoto.com hide caption

itoggle caption iStockphoto.com

Researchers studying brains want to know what's happening in an area called the premotor cortex — the place in the brain that gears up for something the body is about to do, like swimming. Above, Michael Phelps dives off the starting blocks in the final heat of the men's 400-meter individual medley during the 2012 U.S. Olympic Swimming Team Trials in Omaha, Neb., on June 25. Jamie Squire/Getty Images hide caption

itoggle caption Jamie Squire/Getty Images

A 3-D model of HIV peeled back to show its layers. HIV's genetic material sits inside a spherical shell (gray matrix) studded with spikes (dark gray and orange). The sphere pops open when a T cell tugs on a spike. Courtesy of Ivan Konstantinov/© Visual Science 2011 hide caption

itoggle caption Courtesy of Ivan Konstantinov/© Visual Science 2011