Cytology is a fundamental discipline in medical sciences that investigates the structural organization, functional mechanisms, and life cycle of the cell as the basic unit of living organisms. This article provides a comprehensive analysis of the main sections of cytology, including cell morphology, molecular organization, membrane transport, organelle specialization, cell cycle regulation, and mechanisms of cell death. Special emphasis is placed on the clinical relevance of cytological knowledge in pathology, oncology, hematology, and regenerative medicine. Modern cytological research methods and their diagnostic significance are also discussed. Understanding cytology at the molecular and ultrastructural levels is essential for interpreting physiological and pathological processes in medical practice.