Recent research from the University of Cambridge has enabled scientists to view critical aspects of embryonic development which were previously unobservable. For several decades, it has only been possible to culture embryos for four days, during which the embryo grows from a single cell to the blastocyst, a ball 64 cells all derived from the first by repeated rounds of cell division. Around the fourth day, the developing embryo implants into the mother’s womb and its development becomes hidden from view as this is taking place. Using the mouse embryo as a model, Professor Zernicka-Goetz and her colleagues, have developed a method that has allowed them to overcome the barrier of implantation into the womb by culturing and imaging embryos outside the body of the mother for the first 8 days of their development.