Cover picture: Agents that alter cell metabolism have a profound effect on mitochondrial structure, dynamics, and function. Using fluorescence microscopy and a dye sensitive to electrochemical membrane potential (), hyperpolarized regions of mitochondria in osteosarcoma cells appear yellow while depolarized regions appear green. (Top left) Under normal physiological conditions, the mitochondrial membrane exists as an interconnected tubular network and the spatial distribution of is heterogenous. (Top right) Addition of a respiratory chain uncoupler leads to uniform activation of throughout the network, while inhibition of respiration (bottom left) leads to its uniform deactivation. (Bottom right) When apoptosis (programmed cell death) is initiated the mitochondrial network is disrupted into giant hyperpolarized vesicles. See the article by Margineantu et al. on p. 1833.