Walter Kohn, born in Vienna, Austria, in 1923, majored in mathematics and physics at the University of Toronto and obtained his Ph.D. at Harvard University. In 1957 he became a US citizen. “For his development of the density-functional theory” Professor Walter Kohn was awarded the Nobel Prize in Chemistry in 1998. His work revolutionized scientists' approach to the electronic structure of atoms, molecules and solid materials. As Professor of Physics, Emeritus and Research Professor at the University of California in Santa Barbara, Kohn is today collaborating with younger colleagues on research in this field. In 2006, Walter Kohn and Alan Heeger realized the film documentation "The power of the sun" that was televised in Austria, Switzerland, and Germany. The two Nobel laureates introduced the viewer to the scientific background of harvesting solar energy and gave an outlook into the future of sustainable energy generation.