Disruption of the embryo shell with a laser beam. Up to the day 6 following fertilization, the embryo is protected by a special coat – zona pellucida. It needs to leave this coat to be able to implant itself in the uterus. If this coat is too strong, it may be the reason why the embryo cannot leave the shell and is therefore not able to implant itself in the uterus. Thinning of the zone on a certain area with a laser beam is safe and poses no risk to further embryonic development.