Live imaging of mitochondria with fluorescent probes unraveled their restless shape restyling all along cell life. Chopping and reconstructing of mitochondrial membranes was soon attributed to large GTPases of the dynamin family and appeared to accompany crucial pathways, from the distribution of mitochondria to daughter cells during cell division, to making release of proapoptotic molecules from mitochondria easier during programmed cell death. Recently, fusion and fission events were shown to apply to other subcellular organelles, including peroxisomes. In addition, proteins modeling mitochondrial morphology were observed on other organelles. A single shared shaping machinery appears to be suitable to the coordination of relevant pathways involving different organelles. Here, we describe our recent discovery of the involvement of the fission protein Drp1 in shaping morphology of the endoplasmic reticulum: morphological defects impinge on ER performances, in particular the ability of the cell to couple ER stress and apoptosis.