Cytology is a universally applicable technique that can be used by both general practitioners and specialists. It enables diagnosis of lesions on surfaces such as the skin, mucous membranes or cervix by smear, and the determination of findings from internal organs by fine needle aspiration. The method is technically both simple and inexpensive and can therefore be used in all parts of the world, regardless of their level of development. This book aims to summarize the essential basics of cytology. At the same time, it provides an overview of non-neoplastic and neoplastic lesions, covering both common and rare manifestations across various body sites. The related virtual Case Collection of more than 500 cases from almost all organs provides deeper insights into the morphological spectrum of lesions and into the cytological literature. It is free to access at Essentials of Cytopathology: Interactive Case Collection