With the help of sperm functional analysis it is possible to determine the maturity of sperm cells and their ability to fertilize an egg. Immature sperm cells do not have the ability to fertilize the egg. Mature sperm cells have sperm head proteins which determine their ability to find an egg and get attached to it. If this does not happen the egg will not get fertilized. Sperm cells which have successfully attached to an egg dissolve the membrane of the egg, in order to reach the external egg membrane. After that, sperm cells and egg interactivity is possible – this is the process of fertilization. With the help of the above mentioned analysis it is possible to detect how many sperm cells are mature and have the ability for egg fertilization.