The first time two-year-old Niklas Mertens climbed on his father’s handmade plywood version of a children’s bicycle and took a ride he attracted a good deal of attention.

“People just gaped,” says Rolf Mertens, then a designer for a computer magazine, remembering the sight of the toddler wheeling about in a pedestrian zone in Aachen, Germany. “They had never seen a two-year-old zip around like that.” Niklas’s mother, Beate, says: “He got on and took off. He only stopped for meals and sleep.”