The history of hybrid cars goes back to the year 1900, when legendary engineer Ferdinand Porsche (yes, the guy that started Porsche) built the Mixte which used individual wheel motors. But it wasn't until 1997 that improved lithium-ion and nickel-metal hydride battery tech allowed the first mass-produced hybrid—the Toyota Prius—to hit the streets. Though plagued with problems at first, the Prius got better and an entire market was born. Every automaker either builds one, or plans to bring one to market. And it's easy to see why: In 2009, hybrids accounted for 2.5% of all American car sales. It's big business, kid.