Many diseases result from a microbe that enters the cells of the body.

A diazotroph is a microbe that lives in the roots of plants, and provides nitrogen to the plant.
People use a microscope to see microbes.

Diazotroph is the common name for nitrogen-fixing bacteria and micro-organisms.

Specifically, the term designates organisms that are capable of turning atmospheric nitrogen into more usable forms, such as ammonia. It includes such soil-dwellers as Frankia genus members living symbiotically with actinorhizal (beech, cucurbit and rose-related orders) plants and Rhizobia genus members living symbiotically with leguminous (bean-related order) plants. Cyanobacteria living symbiotically with lichens and liverworts also number among the diazotrophs of greater name recognition.