This textbook on Protistology provides an excellent information source for a broad audience ranging from students of advanced university courses to senior scientists, for the study of parasitic and/or pathogenic microorganisms; lavishly and unsurpassedly illustrated with about 800 single micrographs, line drawings and diagrams allowing an overwhelming insight into the architectural variety of unicellular creatures and their dynamical properties. The pivotal ecological roles unicellular organisms play in the bionomics of life on earth, at present and in the past as well as the phylogenetic relationships between unicellular and multicellular organisms are thoroughly explained.