Most cells are very tiny, which is beyond the limits of human vision. You must use a microscope to observe cells. However, before the objective existence of cells is realized, it is impossible to know that the object observed under the microscope is cells. Therefore, in 1677, when A.van Leeuwenhoek observed the "sperm" of animals with a simple microscope made by himself, he did not know that it was a cell. In 1667, when R. Hooke observed the slices of cork, he saw that cork contained cell, so he named it. In fact, these cells are not living structures, but gaps formed by cell walls, but the term cell has been used. In the initial stage of cytology, although many tiny objects, such as bacteria and ciliates, were also observed with a simple microscope, the main purpose was to observe some developmental phenomena, such as the metamorphosis of butterflies and the structure of sperm and eggs. Due to the limitation of the microscope at that time, the observation was not accurate enough, and the bondage of religious beliefs, these observation results (16 cytological results) supported the dogma of predestination. Some people claim to see specific and tiny "little people" in sperm, and think that they will develop into future individuals-elitists; Others believe that "little people" exist in eggs-egg-watchers. The influence of predestination lasted for more than 1 years, which prevented people from further understanding cells on the basis of R. Hook. It was not until 1827 that к m. Bell discovered mammalian eggs that he began to carefully observe the cells themselves. The achromatic objective lens developed before and after this, the introduction of carmine and hematoxylin as dyes to stain the nucleus, and the start-up of slicer and slicing technology all created favorable conditions for more detailed observation of cells. It is M.J. Schleiden and T.A.H Schwann who have greatly promoted the study of cells. In 1838, the former described that cells were produced by a crystallization-like process in a mucilaginous matrix, and nuclei were first produced (nucleoli were also found). He also regards plants as the * * * isomorphism of cells, just like the group of hydra. Inspired by him, Shi Wan firmly believed that animals and plants are all made of cells. He accumulated a lot of facts, pointed out their consistency in structure and growth, and put forward the cell theory in 1839. At the same time, Czech animal physiologist J.E. Purkinje put forward the concept of protoplasm; German zoologist C.T.E.von Sebald (1845) concluded that protozoa are all unicellular. German pathologist R.C. Fairshaw (1855) put forward the famous saying that "all cells come from cells" on the basis of studying connective tissue, and founded cytopathology. German zoologist M. Schoultze defined the cell in 1861: "A cell is a protoplasm with all life characteristics, and the nucleus is in it." The above stage can be said to be the foundation stage of cytology. The further development of cytology, first of all, deepened the understanding of cell structure. Because we must have a correct understanding of structures before we can further explore their functions.