They live every where
They can effect you and other organisms
They are microscopic
A through cell division and production
Keratin is an intracellular fibrous protein that gives hair, nails, and skin their hardness, strength, and water-resistant properties. The keratinocytes in the stratum corneum are dead and regularly slough away, being replaced by cells from the deeper layers
Hope this helped!
Good luck :p
~Emmy <3