Joseph Fourier was a young scientist in the employ of Napoleon. He went with Napoleon on his ill-fated expedition into Egypt. It was here that he recorded many observations that lead him to his work in heat transport theory. Later in life - he lived between 1768 and 1830 - he was the prefect in Grenoble and here he wrote his seminal work "Memoire sur la Chaleur" which expounded upon his ideas of heat transfer and outlined his new method of mathematical analysis which we now call Fourier Analysis.
The basic thesis of his theory was that if one had a complete set of
functions, any arbitrary function could be accurately described by a linear
combination of the various members of this complete set of functions. He
provided his proof of this work as his submission for the Paris Prize competition
one year. The judges (who that year were Lagrange, Laplace, and Legendre)
argued that though his work proved that a complete set of functions would
accurately describe many functions, he had not proven that they could describe
ANY function. They were right. He had not proven it. But Fourier
was also right. However, he did not win the Prize that year and it was
many years later that others were finally able to complete the proof. Fourier
analysis is extremely important in modern mathematics and the ideas are
the basis upon which will describe the wavefunction of complex systems
such as molecule and solids.