This document provides an overview of leucopoiesis, the process by which white blood cells are produced. It discusses the classification, morphology, properties, functions, and applied physiology of the main white blood cell types - granulocytes like neutrophils, eosinophils and basophils, and agranulocytes like lymphocytes and monocytes. It also covers pathological variations in white blood cell counts, disorders like cyclic neutropenia and hypereosinophilic syndrome, and recent advances in areas like bone marrow transplantation and flow cytometry.