History
Count Amedeo Avogadro lived from 1776 to 1856 in Italy. He was a lawyer, but later got interested in physics and became a scientist. Avogadro was the first person to propose the idea of molecules. These ideas were vital to the developement of chemistry, and so many years later, this huge number was named after him: Avogadro's Number, N_a. The exact amount of molecules in a mole wasn't known when the word was coined, but we have been getting better precision as the years go on. Albert Einstein got a very accurate amount in 1905. Today, more than ever, the mole plays an important part in chemistry.