Both in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) are fertilization of eggs and sperm outside the body. The difference is the fertilization process. IVF (In-vitro Fertilization) is the fertilization of eggs and sperm in a laboratory. While ICSI (Intracytoplasmic Sperm Injection) involves selecting a single healthy sperm and using a needle to inject it directly into the egg to increase the chances of fertilization.