Monk (IMAGE) University of Vienna Caption This is a Zen monk meditating in front of balancing stones. The stones on the wooden plank represent hematopoietic stem cells reentering quiescence (left) and the production of blood cells (right), respectively. The stack of rocks on which they balance represents the ERK- and MEK1-dependent feedback mechanism. Credit Manuela Baccarini Usage Restrictions The image may only be used with appropriate caption or credit. License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.