embryo cleavage stage embryo Embryo that is in the cleavage stage, which encompasses the first 13 rapid divisions after fertilization, corresponding to embryonic stages 1-4, prior to cellularization (Hartenstein, 1993; Campos-Ortega and Hartenstein, 1997). The first seven divisions are synchronous (Campos-Ortega and Hartenstein, 1997). During the course of the subsequent three divisions, most of the nuclei approach the surface, to form the syncitial blastoderm (Campos-Ortega and Hartenstein, 1997). They then divide asynchronously a further three times, bringing the total number of cells to around 5000 (Campos-Ortega and Hartenstein, 1997). fly_anatomy.ontology FBbt:00000054 FBdv:00000054