Fluorescent protein photoconversion is a powerful approach that can be adapted to investigate various aspects of cellular behavior in diverse contexts. In somatic cells, fluorescent photoactivation of photoactivatable-GFP (PAGFP) has been used to accurately determine the timing of plasma membrane abscission, the final step of cell division that establishes two cytoplasmically separate cells. Diffusion of photoactivated PAGFP from one cell into its sister cell shortly after mitosis indicates that abscission has not occurred, whereas photoactivated PAGFP that will not pass between cells suggests successful abscission. Here we have adapted this approach to enable investigation of abscission timing in the context of early mammalian embryos.