Microsurgical Epididymal Sperm Aspiration (MESA) is a procedure designed to retrieve sperm from the epididymis, a tightly coiled tube located at the back of each testicle where sperm matures and is stored. This technique is often used in cases of obstructive azoospermia, where sperm production is normal but a blockage prevents sperm from being ejaculated. By using microsurgery, doctors can aspirate sperm directly from the epididymis for use in assisted reproductive technologies, such as in vitro fertilization (IVF) with intracytoplasmic sperm injection (ICSI). MESA is known for its high success rates in retrieving viable sperm and is considered when there is a need for a large number of high-quality sperm, especially if sperm freezing for future cycles is anticipated.