The progression in hardware representation of a bit of data: Vacuum Tubes (1950s) - one bit on the size of a thumb Transistors (1950s and 1960s) - one bit on the size of a fingernail; Integrated Circuits (1960s and 70s) - thousands of bits on the size of a hand Silicon computer chips (1970s and on) - millions of bits on the size of a finger nail.
The progression of the ease of use of computers: Almost impossible to use except by very patient geniuses (1950s); Programmable by highly trained people only (1960s and 1970s); Useable by just about anyone (1980s and on).