Size of colloidal clay particle is less than

A colloid is a glue-like organic or inorganic matter with too little particle size but a large surface area per unit mass or volume.
The size of the clay particles is the smallest. It is less than 0.002 mm in diameter.
Moreover, the size of sand is 2.0 to 0.05 mm and Silt is 0.05 to 0.002 mm.