Transistor
The transistor is the fundamental building block of modern electronic devices, and is ubiquitous in modern electronic systems. Julius Edgar Lilienfeld patented a field-effect transistor in 1926 but it was not possible to actually construct a working device at that time. The first practically implemented device was a point-contact transistor invented in 1947 by American physicists John Bardeen, Walter Brattain, and William Shockley. The transistor revolutionized the field of electronics, and paved the way for smaller and cheaper radios, calculators, and computers, among other things. The transistor is on the list of IEEE milestones in electronics, and Bardeen, Brattain, and Shockley shared the 1956 Nobel Prize in Physics for their achievement.
Walter Houser Brattain
Shockley believed (and stated) that he should have received all the credit for the discovery of the transistor. He actively excluded Bardeen and Brattain from new areas of research, in particular the junction transistor, which Shockley patented. Shockley's theory of the junction transistor was an "impressive achievement", pointing the way to future solid-state electronics, but it would be several years before its construction would become practically possible.