Microtubules in live urchin embryos expressing three tandem GFPs fused to the ensconsin microtubule-binding domain (EMTB-3G; Faire et al., 1999). Microtubules approach the cortex everywhere before anaphase onset (1 min, 30 s). During anaphase, just before furrowing, many astral microtubules penetrate both polar and equatorial cortex. Embryos 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 14â€“17°C, which is tolerated well. Related to Figure 1 and video 1 of J Cell Biol. 2009 Dec 14;187(6):831-45.