A semiconductor is a material that can connect and conduct electricity and heat. They are made of materials like carbon, silicon, germanium, and silicon germanium, and are found in computer chips, solar energy cells, and LED lights. The electrical conductivity of semiconductors can be controlled by doping them with other elements, such as phosphorus or boron. This allows for the creation of p-type and n-type semiconductors, which are the basic components of transistors. Semiconductors are also the materials used to make silicon chips, which are the heart of modern electronics. The first transistor was made from a germanium semiconductor in 1947. Today, semiconductors are used in a wide range of electronic devices, including computers, cell phones, and LED lights.