A fusion reactor is a device designed to harness the energy produced by nuclear fusion, the process where atomic nuclei combine to form a heavier nucleus, releasing a significant amount of energy. This process is similar to what powers the sun and other stars, making fusion a potential source of clean and virtually limitless energy for the future. In a fusion reactor, isotopes of hydrogen, such as deuterium and tritium, are typically used as fuel. When these isotopes are heated to extremely high temperatures, they collide and fuse, creating helium and releasing energy in the form of heat. This heat can then be used to generate electricity, offering a promising alternative to fossil fuels and reducing greenhouse gas emissions.