Zona pellucida is the structure to protect embryo cell, and embryos must be released from the zona pellucida before endometrium is implanted. This process is called Hatching. Under some circumstances, zona pellucida incrassation would make embryo difficult to be naturally hatched, so embryo assisted hatching technology is to make use of artificial help to complete the release of zona pellucida, so as to improve the success rate of embryo implantation. In general, assisted hatching uses laser to open a trumpet-shaped hole in zona pellucida to help embryo cell release from zona pellucida.