It is the most commonly used test in clinical laboratories. It is mainly used for quantitative, qualitative and morphological tests on cells and other components of various body fluids, such as blood, urine, stool, plasma fluid and cerebrospinal fluid, and secretion specimens, for disease prevention, diagnosis, differential diagnosis and prognosis. It provides an objective laboratory basis for disease prevention, diagnosis, differential diagnosis, efficacy monitoring, and prognosis. In the past, most of the clinical tests were performed by traditional manual methods, i.e., by microscopic examination of cells and their organic components. With the rapid development of automated analyzers, modern testing instruments have increasingly replaced manual methods with their advantages of rapidity, simplicity of operation, reproducibility, multiple parameters, ease of accusation, and large amount of information. However, for the testing of abnormal specimens, instrumental testing cannot yet completely replace manual testing.