When our homes get hot, we tend to react by cranking up the air conditioning. Sure, the AC will cool things off in a hurry, but it's really not a very energy-efficient way to control your climate. In today's energy-challenged world, efficiency is key.

What to do? Think smart window technology. At least, that's what many scientists and engineers have been doing. Specifically, they've started thinking about how to make windows more useful when it comes to conserving energy.

One promising technology uses chemicals and electricity to make windows that can darken and lighten at the flick of a switch. To create what's called an electrochromic window, you coat the glass with a chemical compound like tungsten oxide. This compound is naturally opaque, but you can make it appear clear by applying a small jolt of electricity. One great thing about this method is that you don't need a constant source of electricity to power the window. A small, brief jolt is enough to darken a clear electrochromic window, for example. The windows stays dimmed until another jolt is used to make it more or less dim. Using this and other techniques, scientists are working to create windows that we can dim as much or as little as we like.

Due to manufacturing costs and other issues, the widespread use of smart windows is still a ways off. However, being able to completely block sunlight from entering empty rooms and buildings will do a lot to cut down on the costs of escaping the heat. Now that's pretty cool.