Parasitology is the scientific discipline concerned with the study of parasites, their hosts, and the intricate relationship between them. As a field within biology and often overlapping with microbiology, it encompasses the study of a diverse range of organisms, from single-celled protozoa to complex multicellular helminths (worms) and arthropods that live on or inside another organism to their own benefit. Key areas of investigation include the parasite's life cycle, the mechanisms of disease they cause (pathogenesis), the host's immune response, and the development of strategies for diagnosis, treatment, and control of parasitic infections in humans, animals, and plants.