Life begins with a single fertilized cell that gradually transforms into a multicellular organism. This process requires precise coordination; otherwise, the embryo could develop serious complications. Scientists at ISTA have now demonstrated that the zebrafish eggs, in particular their curvature, might be the instruction manual that keeps cell division on schedule and activates the appropriate genes in a patterned manner to direct correct cell fate acquisition. These insights, published in Nature Physics, could help improve the accuracy of embryo assessments in IVF.