A French-Italian mathematician and astronomer, Lagrange was born as
Guiseppe Lagrangia, in Turin, Italy. He became attracted to mathematics
and astronomy after reading an article by the astronomer Halley. At the
age of nineteen he was appointed a professor at the Royal Artillary
School in Turin. He communicated some of his mathematical discoveries to
Euler and, by age twenty-five, he was regarded by some to be the greatest
living mathematician.In later years, after moving to France, he was greatly admired by Napoleon. One of his greatest achievements was the application of mathematics to problems in celestial mechanics (the motion of heavenly bodies as a result of gravitational forces) and the development of a branch of mathematics called Calculus of Variations (which is precisely the technique now used to solve problems such as Johann's Bernoulli's Brachistochrone Problem).
In spite of his fame, he was a shy and modest man.
He also married a sixteen-year-old when he was in his fifties!