A particle and a composition including a plurality of particles are provided, wherein the particles are platelets exhibiting a planar geometry which is circular or which is made up of a number (x) of planar (y)-sided polygon(s), wherein x is from 1 to 20 and y is at least 3 wherein if x is greater than 1 then said planar (y)-sided polygons are fused along one or more sides thereof, wherein the width (WP) of the platelets (P) at their widest point is no more than about 250 pm and the thickness of the platelets (P) is in the range of 10 nm to 50 nm.