Daughter cells maintain their division orientation as they migrate after most divisions. ES cell–derived vessels (WT; Tg PECAM H2B-GFP) were imaged, and after divisions were scored (i panels) the 2 daughter nuclei (pink) were followed for 1 to 2 hours further. The numbers in the lower right represent elapsed time in minutes. In all cases ii panels show the final image scored. The iii panels diagram the movement of each daughter nucleus (shown in pink) after division: one daughter nucleus is tracked with a green line and the other with a pink line. The vessel is shown by black lines, the vessel long axis is shown by the broken blue line, and the division angle is shown by the broken orange line. (A) A division perpendicular to the vessel long axis, where the daughter cells maintained the division orientation after 1 hour (n = 61 of 61). (B) A division parallel to the vessel long axis, where the daughter cells maintained the division orientation after 1 hour (n = 7 of 10). (C) A division parallel to the vessel long axis, where the daughter cells changed position relative to the division orientation after 102 minutes (n = 3 of 10).