Why do some people, like David Bowie, have different-colored eyes?
There are hundreds of reasons why someone might have two different-colored eyes, known as hetero-chromia, says Dr. Richard Hertle, a pediatric opthamologist at the National Eye Institute in Bethesda, Maryland. Two of these are direct injury to the eye or an underlying disease that affects the eyes.
Five amazing, clean technologies that will set us free, in this month's energy-focused issue. Also: how to build a better bomb detector, the robotic toys that are raising your children, a human catapult, the world's smallest arcade, and much more.