3-D imaging reveals a highly connected network of muscle mitochondria (green). Blue, nucleus (N); magenta, capillary (V); red, red blood cell. PVM, paravascular mitochondria; IFM, intrafibrillar mitochondrial network. (Reprinted by permission from Macmillan Publishers, Ltd. B. Glancy et al. Nature. http://dx.doi.org/10.1038/nature14614, copyright 2015.)