Nails start in the nail root, hidden under the cuticle. When cells at the root of the nail grow, the new nail cells push out the old nail cells. These old cells flatten and harden, thanks to keratin, a protein made by these cells. The newly fromed nail then slides along the nail bed, the flat surface under your nails.
Answer:
Adaptations and selective breeding, if that is a choice for you.
Explanation:
Protons and Neutrons affect the mass. Protons and Electrons change the charge of the atom (positively or negatively charged). Valence electrons are the ones that do fun stuff in chemical reactions, they are responsible for making/breaking bonds, at least to my understanding.
Hope this helps.