This review provides background and perspective for the articles contributing to the Special Issue of MDPI Micro-organisms on Paramecium as a Modern Model Organism. The six articles cover a variety of topics. each taking advantage of an important aspect of Paramecium biology: peripheral surface proteins that are developmentally regulated. endosymbiont algae and bacteria. https://www.parisnaturalfoodes.shop/product-category/magnesium-potassium-aspartates/