Rainbow Nonpareils (or hundreds and thousands outside North America) are a decorative confectionery of tiny balls made with sugar and starch, traditionally an opaque white but now available in many colors.
Their origin is uncertain, but they may have evolved out of the pharmaceutical use of sugar, as they were a miniature version of comfits. The French name has been interpreted to mean they were "without equal" for intricate decoration of cakes, desserts, and other sweets, and the elaborate pièces montées constructed as table ornaments.
Put them on your cakes and desserts for a festive touch.