Eight-cell purple urchin embryo expressing three tandem GFPs fused to the ensconsin microtubule-binding domain (EMTB-3G; Faire et al., 1999). The embryo was treated with 20 µM nocodazole at time 00:00. Within 2 min, most astral microtubules disassembled; remaining microtubules are randomly oriented and most end well short of the cortex. Even so, furrowing is accurate and timely. Purple urchin were imaged with a laser scanning confocal microscope (Radiance 2000; Bio-Rad Laboratories) mounted on a compound microscope (E800; Nikon) using a 40× 1.3 NA Plan-Fluor oil lens. Room temperature was maintained at 14–17°C, which is tolerated well. Corresponds to Fig 3A and first segment of video 3 in J Cell Biol. 2009 Dec 14;187(6):831-45.