I have a head and a sharp end, but I am not an animal. A hammer helps me do my job. What am I?

In science I measure, in earth I reside, on skin I appear, though small I may hide. From numbers to tunnels to marks you can see, one word defines all versions of me.

I sit on shirts coats and machines waiting for a push or a press to wake up. I hold fabric together or switch on a light with a single tap of your finger. I come in many colors shapes and sizes yet I never move on my own unless someone decides to press me. From old cardigans to modern keyboards I am always there ready to be pushed again. What am I?

Black tears of the void, Words bloom on pale paper fields, Stories stain the page.

Attach with adhesive, Simple dog toy, Stay together now! A car? Oh, boy!