Movie 1.

Representative z-stack views through WT 3DMOUSEneST implantation site scans at E4.5, E5.5, and E6.5. From left to right: z-stack images taken across WT E4.5, E5.5, and E6.5 implantation sites. SHG (gold) is visualizing fibrillar collagen of both the decidual nest and the myometrium. THG (blue) provides context to outline the conceptus (darker ‘hollow’ in the middle of the scans). An asterisk indicates the conceptus position, shown in the top-tobottom z-stack series, but is excluded from the subsequent bottom-to-top z-stack series for unobstructed conceptus viewing. Scale bars for all are 300 μm. AM, antimesometrial; E, embryonic day; M, mesometrial.