It may be a while before this new engine hits the road, but it’s incredibly cheap to build and could lead to a serious shift in the way we think about transportation. According to the Washington Post, the prototype presented by researchers at Columbia University can run on nothing but evaporating water and bacterial spores.

The team of scientists unveiled a number of prototypes in a study published in Nature Communications this Tuesday. Though they are simple in design, the mechanism used to create energy certainly isn’t. The devices use the shrinking and bloating of certain bacterial spores as a result of changes in humidity to their advantage. Researchers say that they’ve only just started to unlock the technology’s energy potential.

Lead author and associate professor Ozgur Sahin has been studying bacterial spores for quite some time now. After nearly a decade of work studying bacterial spores, he is just beginning to exploit the spores’ responses to changes in humidity for the purpose of generating energy.

“People before us had shown that the spores change shape in response to humidity. They shrink when they’re dry and expand when exposed to moisture,” Sahin explained. He noticed how rigid the spores were under dry conditions, which meant that the shift in shape must be the result of a significant energy change.

Sahin sketched out an idea where a device rested on the surface of a body of water. Shutters would control the flow of moisture throughout the system, exposing spores to a controlled level of humidity. When the spores became too dry, they would close the shutters and increase the moisture present. When they became too moist, the spores would expand and open the shutters. This would create a type of perpetual motion that is almost entirely self-regulated.

So far, Sahin and his team have developed devices that can turn light bulbs on and off using the spores, as well as an engine that can power a miniature car. Though the devices seem like toys, they can be significantly scaled up for a wide range of industrial applications.

Without further ado, you can watch the car in action here: