Assisted hatching is a special technique used as an assisted reproductive technology. A protective coating, called the zona pellucida, shields the developing embryo as it travels through the fallopian tube and enters the uterus. In order for the embryo to attach to the uterine wall, the zona must be dissolved and the embryo released. This is a naturally occurring process called embryo hatching. Assisted hatching was developed to overcome barriers to this process due to zona hardening or thickening. The zona can be penetrated using chemical agents, mechanical pressure, or a laser to assist in the release of the embryo and to promote implantation.