Animation of the inside of a hydrogen fuel cell, showing the process by which it generates electricity. The fuel cell comprises an anode layer and a cathode layer, separated by a membrane. Hydrogen is introduced at the anode side, and oxygen at the cathode. A catalyst splits the hydrogen into two protons and electrons. The membrane allows the protons through to the cathode, but forces the electrons down a wire. The flow of electrons through the wire can perform electrical work, such as lighting the light bulb here. On the cathode side, the protons and electrons react with an oxygen atom, forming water. The fuel cell will keep generating power in this way as long as it is supplied with fuel. This clip is available without labels as K004 4846.