Time-lapse images of nuclear division cycle in embryos expressing ERsp-RFP–KDEL (ER, red) and lamin B–GFP (nuclear envelope, green) under the control of the G302-Gal4 maternal driver. The ER extends from the nuclear envelope as indicated by the merged image (t = 00:00, merged, yellow). As nuclei enter mitosis (t = 01:00–03:00, green), a partially disassembled lamin B envelope can be observed, whereas the ER is continuously present throughout the cell cycle (red). The nuclear envelope is reassembled at telophase (t = 04:00, green).