the.com/microbe

means A microscopic living organism — bacteria, viruses, fungi, and the like — too small to see without a microscope but big enough to run your gut or wreck your lungs.

from Coined in the 1870s–80s by fusing Greek 'mikros' (small) with 'bios' (life) — scientists needed a tidy word for the tiny organisms germ theory was suddenly proving mattered enormously. French surgeon Charles-Emmanuel Sédillot is usually credited with popularizing the term around 1878, giving the invisible world a name right as microscopes and Pasteur's work were making it impossible to ignore.