This is a great question. As we mentioned in our Up, Up, and Away video, the helium we have today comes from natural gas deposits, some of the largest of which are in the U.S. But how did the helium get there? Well, mostly from radioactivity. As certain radioactive elements, like uranium, decay, they release a type of radiation called Alpha Particles. Alpha particles are basically helium atoms only without electrons. When this decay happens deep in the Earth, the alpha particles pick up electrons and become helium. Then, the helium gas is captured under impermeable rock layers, like those that hold natural gas.