Mouse blastocyst 3.5 days after fertilisation

Confocal micrograph of a pre-implantation stage embryo collected from the uterus of a female mouse approximately 3.5 days after fertilisation. At this stage of development, the embryo is a bundle of cells and is known as a blastocyst. This early blastocyst, which is approximately 80 microns in diameter, has been labelled with two dyes that allow individual cells within the embryo to be visualised. These dyes stain the nucleus of each cell (DAPI; blue) and the membrane that surrounds each cell (Alexa Fluor Phalloidin; red). A series of optical sections have been reconstructed and rendered to form this 3D image.