The smallest unit of matter that has the characteristic properties of it’s element is called an “atom”.
Individual atoms are called “elements” for that reason.
There are smaller divisions of matter, however those no longer have the characteristics of the element that they may be a part of. A hydrogen electron is indistinguishable from an argon electron, or any other.
First cousins share a grandparent, second cousins share a great-grandparent.
Once retinal has absorbed a photon which initiates effects that create nerve impulses, the impulses get carried to the brain, which then processes the impulses along with other signals, ultimately allowing the eyes to see.
