Computers were developed for research in the 1930s and were used to break codes in World War 2. Large vacuum tubes made them huge but in the 1950s these were replaced with transistors. In the 1960s computers became even more compact, as a result of microchip technology.
Today there are desktops, laptops and even handheld computers that are more powerful than the early house-sized computers.
The video below gives a brief background to the one of the oldest computers - Colossus.