One side is for birth to 3 months -- with high-contrast black, white red illustrations for early visual stimulation -- the other for 3 to 6 months with brightly colored, more complex 3-D figures & activities, to entice baby to tummy-time play. The highly contrasting, strong-color (black, white red) illustrations on one side, & the more complex, more colorful illustrations on the other side, accompany baby as his sense of sight develops over the first few months of his life.