0 a living thing that on its own is too small to be seen without a microscope -- microorganismo
1 a very small living thing that is only visible using a microscope, for example bacteria. -- microorganismo
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.