While most other cells are made of silicon, multi-junction cells contain a combination of III-V semiconductors, which include gallium, arsenic and indium. The outstanding efficiency of these tiny cells is down to more than just their high quality. They also get an unusually large amount of sunlight. Special lenses concentrate the solar radi-ation to 500 times its normal intensity. A single panel is made up of dozens of cells and lenses. The panels are mounted on frames that keep them facing the sun. Small power plants with several hundred kilowatts of capacity are already in operation in the US and Spain.