Question

things we cannot see

Answer 1

we cannot see the bacteria viruses many micro organism with our naked eyes because they are very small in size we need microscope to observe them

Answer 2

Explanation:

There are numerous things that we cannot see.
There is a never ending list of things we cannot see, some of them being the following:

1) Natural elements: Air, Elements such as oxygen, carbon dioxide, hydrogen, helium, etc.
2) Emotions or Feelings: Love, Hatred, Fear, Kindness, Jealousy, Generosity, Honesty, etc.
3) Sensation: Hotness, Coldness, etc.
4) Microorganisms: Bacteria, Fungi, Amoeba, Paramecium, Virus, Pathogens, etc.
(Note: Microorganisms can be seen with the help of a microscope.)

And the list can go till infinity, denoting the utter omnipresence of a number of things that cannot be seen, but can only be felt.