Contents

25 February 2000
Vol 287, Issue 5457

About The Cover

Cover image expansion

COVER Stem cells can follow a variety of blueprints directing cell differentiation. But the final edifice is not built of stone, and differentiated cells show remarkable plasticity. See the special section on stem cells, beginning on page 1417, for information about the research, therapeutic implications, and ethical concerns relating to stem cells. [Illustration: Carin Cain]