This document discusses microbes and their importance to human welfare. It defines microbes as living organisms too small to see with the naked eye that are visible under a microscope. It notes that Anton van Leeuwenhoek discovered microbes in 1675 using one of the first microscopes. The document provides examples of how microbes are used to produce important household products like bread, cheese and beer, as well as industrial products like ethanol and antibiotics. It also discusses how microbes are used to produce bioactive molecules and how some microbes aid soil fertilization.