Illustration depicting mitochondrial fission. This process creates new mitochondria and also acts as quality control to remove defective mitochondria. Mitochondrial fission begins with the endoplasmic reticulum (ER, blue) being recruited to the constriction site. Dynamin-related protein 1 (DRP1, green) is recruited from the cytosol to the mitochondria surface to aid in the ER-mediated constriction. The constriction of the mitochondrion is then aided by DRP-1 and actin (red). This causes the splitting of the mitochondria, generating two new mitochondrion. This images is the first of three images, please see F033/6272 and F033/6273.