The compact caterpillar unfolds to become two fun number exercises for youngsters: on one side, the numbered panels of the caterpillar's body open to reveal countable groups (from 1 bicycle all the way up to 8 spider legs, 9 ladybug spots, and 10 fingers) and the spelled-out name of the number. On the reverse, each train boxcar carries acountable cargo-one monkey, two trucks, three cows. A sturdy slipcase protects the book from wear and tear.