Clausius was one of the founders of thermodynamics. His most important paper, on the mechanical theory of heat, published in 1850, first stated the basic ideas of the second law of thermodynamics. In 1865 he introduced the concept of entropy.
Clausius graduated from the University of Berlin in 1844, and got his doctorate from the University of Halle in 1848. He then taught in Berlin, Zurich, Wurzburg, and Bonn.
His wife, Adelheid Rimpham, died in childbirth in 1875, leaving him to raise their six children. He continued to teach, but had less time for research thereafter.