The transistor was invented in 1926 by Julius Edgar Lilienfeld though it was not possible to actually construct a working device at that time. It is a semiconductor device and piece of electronic hardware used to amplify or switch electronic signals and electrical power, and it has 3 terminals.
Transistors were revolutionary in the field of electronics and paved the way for smaller technology. They replaced vacuum tubes, allowing the Transistor computer to perform the same functions as a computer but with less power and space.
One interesting fact about transistors is that they are the most widely manufactured device in history. The two main types of transistors are bipolar and field-effect.