Philip Siekevitz, an Emeritus Professor at the Rockefeller University who made pioneering contributions to the development of modern cell biology, passed away on December 5th, 2009. He was a creative and enthusiastic scientist, as well as a great experimentalist who throughout his lifetime transmitted the joy of practicing science and the happiness that comes with the acquisition of new knowledge. He was a man of great integrity, with a thoroughly engaging personality and a humility not often found in people of his talent.