“Journey to the Microcosmos: Paramecium--The White Rat of Ciliates” explores paramecia as model organisms in microbiology. The video explains how these unicellular eukaryotes use cilia for movement, contain macro- and micronuclei, and live in freshwater, brackish, and marine environments worldwide. It highlights key concepts including morphology, genetics, reproduction, endosymbiosis, cryptic species, genome sequencing, and polarized light microscopy. The episode also examines how scientists classify paramecia, why globally distributed species show little genetic variation, and how bacteria linked to the “killer trait” changed scientific understanding. With references to researcher Tracy M. Sonneborn and the scientific process, the content supports life science curricula focused on cells, heredity, evolution of scientific ideas, and microscopy. Part of the "Journey to the Microcosmos" series.