Yeah, I'm a thief . . . I got this from nomad:

At age 21:

Italian violinist and composer Giuseppe Tartini had a dream in which he sold his soul to the Devil. The piece he wrote upon waking, the "Devil's Sonata," was the best he ever wrote, though far inferior to the one he heard in his dream.

American novelist Herman Melville jumped ship and spent a month as the captive of a cannibal tribe. This became the source of his novel Typee.

Jack London went to the Klondike with the first rush of gold-seekers, returning home a year later as poor as when he had left.

English chemist Humphry Davy discovered nitrous oxide ("laughing gas", and suggested that it may have use as an anaesthetic.

Thomas Alva Edison created his first invention, an electric vote recorder. After it failed to sell, he decided to devote his energy to inventions for which there was a market.

John Dillinger robbed a grocery store, was caught and spent 9 years in prison. He later became "public enemy number one," before being gunned down by the FBI.

Luther Burbank purchased 17 acres of land near Lunenburg, Massachusetts and began a plant-breeding career that would span 55 years.

Pablo Casals made significant modifications in cello playing technique and was acclaimed as a master.

Pittsburgh songwriter Stephen Foster wrote "Oh! Susanna!" which quickly gained great popularity.

Future robber baron Jay Gould began investing in the leather business and speculating in railroad stocks.

Robert Browning publishes his first poetry; it is poorly received.

Alfred Tennyson publishes his first poetry; it is poorly received.

College dropout Steven Jobs co-founded Apple Computer.

French mathematician Evariste Galois developed group theory (and many other theorems) before his death at the age of 21.