Its cells usually contain tannins or other substances that make it dark in colour and sometimes aromatic.
One reason why skin is not normally transparent is that the different substances that make up skin interact with light in different ways.
Age and sex hormones also influence the proportions of the waxy or oily substances that make up sebum, including glycerides, free fatty acids, wax esters and cholesterol.
He distinguished two substances that make up an organism: the soma, which comprises most body parts and organs, and the germ plasm, which contains the cells that give rise to the gametes and hence to progeny.
Don Catlin, the former head of U.C.L.A.'s Olympic Analytical Lab, said that even athletes who take benign supplements could expose themselves to banned substances that make their way into products without being clearly labeled or identified.
He said that when we are born, we are all given a vat full of drink, and at the bottom of this vat was horrible sediment, and assorted toxic substances that made us feel awful.
The interplay between density variations in matter and gravity dictates that the Earth's core (once formed) must remain firmly fixed, and so too must the lighter substances that make up the lithosphere.
This notion seemed to imply determinism and thus to undermine human freedom as did Leibniz's conception of monads, the soul-like individual substances that make up the universe, as in a sense "containing" all of their pasts and futures.
This apparently slight detail has remarkable consequences: it is largely responsible, for instance, for the structure of the periodic table and hence for the pattern of the compounds that the elements can form and for the properties of the substances that make up the tangible world.
There are dozens of cell types, and you can toggle the visibility of numerous proteins and substances that make up the cell.
