Cover picture: Three-dimensional model obtained by electron tomography of a brain mitochondrion from Drosophila with a mutation in the mitochondrial gene encoding subunit 6 of ATP synthase. The outer membrane is red, the inner boundary membrane is yellow, and cristae are white. The cristae are highly unusual, appearing as dilated spherical compartments on the mitochondrial periphery and flattened lamellae in the anterior. For details, see the article by Celotto et al. in this issue pages 810–820.