Colour by Numbers painting kits were initially designed for children in the 1950's to help improve motor skills, increase confidence, and help with concentration. Later, Founder of the PBN concept, Max Klein and artist Dan Robbins, decided the kits could be marketed to adults. Dan Robbins proposed the first kit for the adult market to be rendered in the Cubist style of Pablo Picasso and Georges Braque. However, it was quickly discovered that the adult consumers of the product strongly disliked abstract imagery and preferred the realism of classical landscapes and domestic animals. When the change was made from abstract to realism, sales skyrocketed throughout the 60's and 70's. Today vintage Paint-by-Number paintings are collectible, and sometimes exhibited in galleries and museums as an example of Mid-century pop culture and beginnings of mindless conformity.