Homogeneous mixture that does not settle out upon standing reflect light is an element. solid. hydrated.

Homogeneous mixture that does not settle out upon standing but which will reflect light is called COLLOIDS.
There are three types of homogeneous mixtures, these are: solutions, colloids and suspension. Colloids are usually distinguished by Tyndall effects. Light passing through a colloidal dispersion will be reflected.

They carry out the exchange of gases as we breathe ( oxygen and carbon dioxide).