The eggs obtained after egg retrieval (OPU) are surrounded by cells called cumulus.  These cells are responsible for the maturation of the egg. After the eggs are collected, they are kept in a closed system called incubator for 2 hours without any intervention. Then the cumulus cells around the eggs are removed from the eggs with the help of hyaluronidase enzyme and special cannulae. After this, the maturation stage of the eggs can be understood.