The lower-right side of the T9000 four-door refrigerator can switch from fridge to freezer. To convert the six-cubic-foot section, a user selects the mode on an LCD screen, signaling two compressors and three evaporators to adjust the temperature and humidity levels accordingly. Samsung T9000 Four-Door Refrigerator$3,999
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.