Cover picture: The potential energy landscape of the yeast cell cycle network and biological path to stationary G0/G1 phase in protein state space: The lowest energy state corresponds to the stationary G0/G1 state. The low energy valley marked with the green band corresponds to the biological path (sequentially from state 1 to 13 marked by asterisks, including the G2 phase and the M phase) to G0/G1. See the article by Han and Wang on page 3755.