The two primary types of cells in the human body are prokaryotic and eukaryotic cells. While eukaryotic cells make up the tissues and organs of multicellular organisms, possessing a defined nucleus and organelles, prokaryotic cells are simpler and smaller, lacking a nuclear membrane and most organelles. Eukaryotic cells include all human cells—muscle cells, nerve cells, etc.—that are essential for various bodily functions. Prokaryotic cells, mainly represented by bacteria, exist independently and can have a significant impact on human health and the environment. Their differences underscore the complexity of life forms.