Transistor

The transistor gave birth to the digital age. Without it, we wouldn't have the personal computer, the CD player, the fax machine and countless other devices. Developed in 1947, the transistor replaced hot, bulky vacuum tubes, and was the precursor of the now ubiquitous semiconductors and silicon chips embedded in the compact appliances we commonly use. By 1958 the first integrated circuit — a cluster of transistors on a single silicon chip — was created, heralding the age of modern computing.

Source: http://content.time.com/time/photogallery/0,29307,2026224,00.html