The semen can be seen as free sperm when placed under a four times microscope. Usually we use a microscope with a low magnification of 4x and a high magnification of 12x, or a higher magnification if an oil microscope is used. Under the low magnification, what can be seen swimming like a tadpole is the sperm. Fresh semen needs to be retained for immediate observation. If left for too long, the semen may liquefy and become unobservable. Generally, when observing sperm with a microscope at four times magnification, fixed staining is not required, and routine smear examination is sufficient. When observing sperm, we should observe the vitality and number of sperm to initially judge the quality of semen, and also do further seminal plasma biochemical and other tests for a comprehensive assessment. For fresh semen, within 15-60 minutes of placement, liquefaction does not usually occur, but beyond 60 minutes, most of them will liquefy and lose their normal form.