Vintage cranberry glass bowl

Not milk, but flour suspended in water

A colloid is a mixture of one substance spread out evenly inside another substance. They can be in two different phases or states of matter.

One substance is the dispersion medium, such as water or gas. The other is the dispersed medium, sometimes called the 'internal phase'. This is usually tiny solid particles. Otherwise, if the dispersion medium is a gas, then the internal phase can be either tiny particles or tiny droplets of a liquid.