Intracytoplasmic Morphologically Selected Sperm Injection or IMSI is an advanced variation of Intra Cytoplasmic Sperm Injection which involves inserting morphologically selected sperm into the egg.
Expert biologists in the lab use the precision microscope (with very high magnifying power) to see the internal morphology of sperm and throw away those with abnormalities.
The IMSI increases the chances of fertilization in vitro. The couples are advised to go for it if they have already done several In Vitro Fertilization (IVF) sans success.