Born in Zurich, Switzerland, Kölliker qualified in medicine at Heidelberg in 1842 and later held professorships at Zurich and Würzburg. Celebrated for his microscopic work on tissues, he provided much evidence to show that cells cannot arise freely, but only from existing cells. He was the first to isolate the cells of smooth muscle (1848), as expounded in Handbuch der Gewebelehre des Menschen (1852; Manual of Human Histology): probably the best early text on the subject. He showed that nerve fibers are elongated parts of cells, thus anticipating the neuron theory, and demonstrated the cellular nature of eggs and sperm, showing for example that sperm are formed from the tubular walls of the testis, just as pollen grains are formed from cells of the anthers. Again anticipating modern discoveries, Kölliker believed the cell nucleus carried the key to heredity. His pioneering studies of cellular embryology mark him as one of the founders of the science. His book Entwicklungsgeschichte des Menschen und der höheren Tiere (1861; Embryology of Man and Higher Animals) became a classic text in embryology.