0 a very small living thing, especially one that causes disease, that can only be seen with a microscope -- microbio
1 a very tiny living thing invisible to the naked eye, especially a germ causing disease -- microbio
a new understanding of how this microbe causes disease.
We can complete it step by step however long the road is and it can't be completed however short the road is if you don't even mark your footprint.
Podemos completarlo paso a paso, por muy largo que sea el camino, y no se puede completar, por corto que sea el camino, si ni siquiera marcas tu huella.