Bacteria are microscopic single-celled organisms with simple cellular structures. Despite their simplicity, bacterial cells perform many important biological functions that allow them to survive in different environments. The bacterial cell is surrounded by a cell wall that gives the cell its shape and protection. Inside the wall is the plasma membrane, which controls the movement of substances into and out of the cell. The cytoplasm contains enzymes, nutrients, and ribosomes responsible for protein synthesis. Unlike human cells, bacterial cells do not contain a true nucleus. Their genetic material is found in a region called the nucleoid. Some bacteria also contain small circular DNA molecules known as plasmids, which may carry genes for antibiotic resistance. Many bacteria possess flagella that help them move. Others have pili, which are hair-like structures used for attachment and genetic exchange. Certain bacteria also produce capsules that protect them from the immune system and environmental conditions. Bacteria reproduce mainly through binary fission, where one cell divides into two identical cells. Under suitable conditions, bacteria can multiply rapidly. Bacterial cells perform many useful functions in nature. They help decompose organic matter, recycle nutrients, and support ecosystems. Some bacteria are used in food production and biotechnology, while others may cause disease. Understanding bacterial cell structure is important in medicine because antibiotics often target specific bacterial components such as the cell wall or ribosomes. Continued research on bacterial cells helps scientists develop new treatments and improve healthcare. Al-Mustaqbal University – the first university in Iraq.