A Great Physician
He studied medicine in Montpellier (about 70 km southwest of St. Rémy) and set up practice in 1525, at the age of 22. Doctor Nostradamus began treating victims of the plague that was ravaging Provence during the 16th century. He was innovative and skillful, and was so successful treating extremely ill patients that he gained a reputation as a great healer.
A Prophetical Poet
In 1550 Nostradamus moved to Salon-de-Provence and began writing a series of prophecies in quatrains, four-line rhyming verses. By 1555 he published his work as the Centuries, a book containing 100 verses per section. [A Beyond reader suggests that "Michel moved to Salon in 1547-48. He taught medicine at Montpellier in 1530."]
Nostradamus' Centuries contained over 900 "predictions": descriptions of events that would occur from his current time until the end of the world, considered to be AD 3797. (We'll have to wait and see if he was right about that one.) The book was popular enough that he published an expanded version three years later.
Some of the "predictions" are considered to be fairly clear, but many are in the eye of the beholder. Nostradamus embellished the rhymes with Latin, Hebrew, Portuguese and anagrams. In addition, he neglected to use specific dates, and neglected to apply a sequential order to them, so interpretation is everything.
Some of Nostradamus' "predictions" that are said to have been proven true include details of the French Revolution (which occurred only two centuries later), the rise of Napoléon (about the same time), the Great Fire of London in the 17th century, Hitler and the 1939-45 (Second-World) War, and of course the rise and fall of many European monarchs.
The Royal Astrologer
In the midst of his fame, Catherine de Medicis requested Nostradamus to write the horoscopes of her husband, King Henry II [Kings, Valois], and their children. The "Florentine Woman" was renowned for manipulating and plotting, and a main cause of the celebrated St. Bartholomew's Day Event, so her request for horoscopes could have been for rationalization as much as for prediction. By 1560 her husband was dead, his successor (her first son) was dead, and her second son Charles IX became king under her domination.
Nostradamus moved to Salon-de-Provence in 1547. In 1550, at the king's invitation, Nostradamus became court physician, although the job requirements were more for the metaphysical rather than the physical health of his patrons. The royal physician died sixteen years later, on July 2, 1566, at the age of 63.