Intracytoplasmic sperm injection (ICSI) is the process where sperm is injected directly into an egg to fertilize it in an IVF procedure.
In natural conception and traditional IVF, sperm swim to the egg, attach to the egg's shell, and push through the shell to get inside the egg. Once inside, the sperm's DNA mixes with the female's DNA to create an embryo. This is the process of fertilization. In some cases, the sperm cannot penetrate the egg's shell so ICSI is required to help the sperm get into the egg.