"Embryonic day" refers to the early stages or beginning of something. It implies a time when ideas or projects are just starting to develop and have not yet fully formed or matured. Full definition
It shows a mouse at embryonic day 10.5 and the expression of the Fezf2 gene in the developing cortical vesicles (in blue) at the start of brain development. (kavlifoundation.org)
Dorsal root ganglion (DRG) explants from embryonic day 15 rat embryos (Charles River Laboratories, Wilmington, MA) were isolated as described by Kleitman et al. (1998). (jneurosci.org)
At mouse embryonic day (E) 13.5 (Fig. 4b), PRDM16 protein was expressed throughout the left ventricle but was most prominent in the endocardial and epicardial layers. (mdc-berlin.de)