The dispersed-phase substances have a diameter of b/w approx 5 and 200 nanometers. These substances are generally invisible in an optical microscope, thus their presence may be confirmed using an electron microscope and an ultramicroscope. Homogeneous mixtures with a dispersed phase in same size range may be called colloidal emulsions, colloidal aerosols, colloidal foams, colloidal di... https://www.expertsmind.com/chemistry/colloid-chemistry-homework-assignment-help.aspx