One sperm cell is injected directly into the oocyte to facilitate fertilization.
As described in controlled hormonal stimulation of ovaries the first step is to obtain several oocytes.
ICSI is an effective option for men with low sperm count or sperm can not reach the oocyte successfully.

A single sperm cell is aspirated under a special microscope via a very thin injection capillary and injected directly into the oocyte. This microinjection simulates the natural process where a sperm cell forces its way into the ovum.

The procedure has no effect on the fusion of the sperm cell and ovum nuclei. If fertilization and cleavage have taken place, the embryo or blastocyst is transferred into the uterus after two to five days as in the IVF procedure.