RT Journal Article SR Electronic T1 Staging of gastrulating mouse embryos by morphological landmarks in the dissecting microscope JF Development JO Development FD The Company of Biologists Limited SP 1255 OP 1266 VO 118 IS 4 A1 Downs, K.M. A1 Davies, T. YR 1993 UL http://dev.biologists.org/content/118/4/1255.abstract AB We describe and illustrate a set of morphological landmarks for classifying mouse embryos by gross morphology from before gastrulation to the beginning of organogenesis. These landmarks are visible at the resolution of the dissecting microscope in embryos that are intact except for reflexion of Reichert's membrane. Adoption of these criteria should facilitate interpretation of both the expression patterns of genes and the consequences of experimental manipulation of embryos during early postimplantation development.