What is the fundamental electronic component for controlling the flow of electricity?

Transistor

The transistor, invented in 1947 by Bardeen, Brattain, and Shockley, is often considered one of the most important inventions of the 20th century. Before the advent of the transistor, electronic devices used bulky, less reliable, and more energy-consuming vacuum tubes. The transistor revolutionized electronics by making devices smaller, lighter, and more energy-efficient. This invention paved the way for the era of modern electronics, making possible everything from computers and mobile phones to satellites and space probes.