Monash University Living structures that model early human embryonic development have been generated entirely from cells in the skin. The models mean it should be possible to study infertility, early miscarriage and early embryonic development without the controversial use of real human embryos – although the models may raise ethical issues of their own. Previously, the only means of studying the early development of human embryos was via blastocysts obtained from IVF procedures. Blastocysts are a ball-like early stage of embryonic development that is formed five days after fertilisation occurs and can go on to form embryos. But their use in science is controversial because of their potential to grow into a living human individual.