The transistor was invented at Bell Telephone Labs in 1947 by William Shockley, John Bardeen, and Walter Brattain. Transistors are made of silicon with small amounts of impurities added. The photo shows a picture of this first prototype transistor, which was an inch or two square. Today, individual transistors are packaged in a metal can about the size of your thumbnail with three wires running into it.
In simple terms, a transistor, like a vacuum tube, is an electric switch: a current applied to one wire determines whether or not current can pass between the other two wires. Transistors use much less power than tubes and can be switched much more quickly. Transistors can be made very small, and can be integrated on a single chip, meaning we can combine thousands of transistors into a package the same size as an individual transistor. This invention has allowed computers to progress from room-sized monstrosities, to