Josiah Willard Gibbs, who is regarded as one of the founders of physical chemistry, was for many years Professor of Mathematical Physics at Yale. At a time when the technology of steam engineering was half a century ahead of its theoretical understanding, Gibbs applied his brilliant mind to the complex problems of thermodynamics. His most famous contribution was the "phase rule" or law determining the number of physical phases or states possible in a specific system in equilibrium. In 1901 he received the Royal Society's coveted Copley Medal for his work in theoretical science. Gibbs was a shy and retiring man, and his work was little understood in his own time. Only today is his name receiving the just fame it so richly deserves.