Cytoplasm is a colloidal suspension of macromolecules and ions in which organelles are supported by the filamentous cytoskeleton. A colloid is a type of mixture half-way between a homogeneous solution and a heterogeneous mixture. A colloidal suspension contains particles that are of a larger scale than atoms or molecules but smaller than the naked eye. Many familiar substances are colloids, such as milk, paint, and glue.