A microbe, or microorganism, is a microscopic organism that comprises either a single cell (unicellular); cell clusters; or multicellular, relatively complex organisms.  The study of microorganisms is called microbiology, a subject that began with Anton van Leeuwenhoek's discovery of microorganisms in 1675, using a microscope of his own design. Table Of Content : 1 Introduction to Microbiology 2 Chemistry 3 Microscopy 4 Cell Structure of Bacteria, Archaea, and Eukaryotes 5 Microbial Metaboli