The Farnsworth Fusor is a type of device that uses electric fields to heat and fuse atoms — essentially a homemade fusion reactor. It was invented in the 1960s by Philo T. Farnsworth, the same brilliant inventor behind the television.

Unlike massive, multi-billion dollar fusion projects (like tokamaks), the Fusor is small, simple, and has even been built by high school students. But there’s a catch: it produces fusion, but not net energy — it always consumes more power than it generates.