This document provides an overview of the protist phylum, which includes the most primitive eukaryotic organisms. It describes four main classes of protists: Rhizopoda, which use pseudopodia for locomotion and have a single nucleus like Amoeba; Flagellata, which use ribbon-like flagella and may contain photosynthetic pigments like Euglena; Sporozoa, which are endoparasitic and lack locomotory structures like Plasmodium; and Ciliophora, which use multiple hair-like cilia for movement and have both a large meganucleus and small micronucleus.