Leonardo da Vinci, The Vitruvian Man, circa. 1490. The Man's navel, the exact center of his body, is the motionless point where the artistic and scientific individuality cultivated by the Renaissance had its symbolic origin -- the timeless pivot of life's compass.
A microscopic view of a colony of original human embryonic stem cell lines from the laboratory of James Thomson at the University of Wisconsin. Photo courtesy of Jeff Miller, University of Wisconsin-Madison.
