fingernails shouls not curl under or it just depends on how you would like your nails
because they get the hiccups
picking warts on your bum and casual worms.
Yes, fingernails have germs under them.
Sunlight causes this.
smoking
dirt
Stink bugs
Some premature babies get dark colored or black fingernails because of the lack of fat under the skin which causes the skin to discolor. This can also be due to a lowered amount of oxygen in the extremities shortly after birth.
this question is not clear therefore i cannot not answer explain your answer more clearly Under developed muscle, I think...logical.
The deep *vertical* lines in your fingernails are genetic. If you have *horizontal* ridges in your nails, you should see a doctor.
The moon.