Cytology is a branch of biology that studies the morphology, structure and function of cells, as well as biology related to cell growth, differentiation, and evolution. The physiological functions of organisms and all life phenomena are expressed with cells as the basic unit. Therefore, regardless of the understanding of the genetics, development, and physiological functions of organisms, cytology is essential for pathology, pharmacology, etc., as the basis of medical treatment, and agricultural breeding.
Any biological phenomenon comes from the function of cells, so all fields of biology are related to cytology. The independence of cytology as a discipline is from the establishment of M. J. Schleiden (1838) and T. Schwann's (1839) cell theory began. With the development of biological tissue culture, microdissection, electron microscopy, ultraviolet microscopy, phase contrast microscopy, ultracentrifugation, and freeze-drying technology, the physiological functions of cell structure, mitosis, intracellular osmotic pressure and cell membrane permeability have been developed. The theory of this aspect has been developed and confirmed. After entering the 20th century, the application of cytology has attracted more and more attention.