There are two ways that an egg may be fertilized by IVF: traditional and ICSI. In traditional IVF, 50,000 or more swimming sperm are placed next to the egg in a laboratory dish. Fertilization occurs when one of the sperm enters into the cytoplasm of the egg. In the ICSI process, a tiny needle, called a micropipette, is used to inject a single sperm into the center of the egg. With either traditional IVF or ICSI, once fertilization occurs, the fertilized egg (now called an embryo) grows in a laboratory for 1 to 5 days before it is transferred to the woman?s uterus (womb).