what is bleach made from?

it comes from bleach trees

Common chemical bleaches include household chlorine bleach, a solution of approximately 3–6% sodium hypochlorite (NaClO), and oxygen bleach, which contains hydrogen peroxide or a peroxide-releasing compound such as sodium perborate, sodium percarbonate, sodium persulfate, tetrasodium pyrophosphate, or urea peroxide together with catalysts and activators, e.g., tetraacetylethylenediamine or sodium nonanoyloxybenzenesulfonate. Bleaching powder is calcium hypochlorite.

If you mean the manga, it was made form a guy who had this awesome talent that express his imagination in a piece of paper named Tite Kubo.

manga writers. (since its in comic & animation)

A bleach is a chemical that removes colors or whitens, often via oxidation. Common chemical bleaches include household chlorine bleach, a solution of approximately 3–6% sodium hypochlorite (NaClO), and oxygen bleach, which contains hydrogen peroxide or a peroxide-releasing compound such as sodium perborate, sodium percarbonate, sodium persulfate, tetrasodium pyrophosphate, or urea peroxide together with catalysts and activators, e.g., tetraacetylethylenediamine or sodium nonanoyloxybenzenesulfonate.
Bleaching powder is calcium hypochlorite.

wiki

The Shinigami.

Atoms, definitely. (be it the washing agent or the manga)

Sodium hypochlorite (NaClO) and water and such.

comes from white people saliva