A thermonuclear bomb, also known as a hydrogen bomb, is a type of nuclear weapon that uses fusion to release a massive amount of energy. It works by combining light atomic nuclei, such as those of hydrogen isotopes, under extreme heat and pressure, which is typically generated by a primary fission explosion. This process results in a significantly more powerful explosion compared to traditional atomic bombs. The design of a thermonuclear bomb usually involves two stages: the primary stage, which is a fission bomb, and the secondary stage, where fusion occurs. The energy produced can be thousands of times greater than that of the bombs dropped on Hiroshima and Nagasaki during World War II, making thermonuclear weapons some of the most destructive devices ever created.