ABOUT MICROORGANISMS The world of microorganisms is vast and contains many types of life forms with many different physical and characteristics. three main groups of microorganisms exist, bacteria, archae and eukaryote, these three groups classify all types of single cellular life forms in to organized groups. members within these three groups possess many different physical and physiological characteristics that set them apart from the other group. each section is this web page delves thoroughly into each category of microbiological life form; use the navigation bar on the left to guide you to your interests.