Sperm motility refers to the ability or strength of sperm activity. Active sperm is the most essential condition for penetrating the cervical mucus, entering the fallopian tube and uniting with the egg cell, and is therefore one of the components of routine semen analysis. Microscopic classification of sperm activity intensity into 3 levels: in situ activity as level 1, curvilinear movement as level 2, and straight and fast advancement as level 3, with level 3 indicating the most vigorous. In-depth studies on sperm activity include microphotography, microphotography, time-lapse photography and computerized sperm motility evaluation systems, but only for research purposes and not for routine examination.