In Yasuní National Park in Ecuador, butterflies enjoy a very unusual drink. The tears of the yellow-spotted river turtle apparently help the butterflies reproduce--and the butterflies help clean off the turtle's face. Read more here. Pete Oxford/Minden Pictures
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.