Mailed to me by Geoff via [www.boingboing.net] :-

On the Make blog, Phil Torrone recaps Modern Marvels’ top 25 inventions of 2006. Shown here: Matthew C. Grossman’s “Shift Bicycle,” designed to teach kids how to ride a two wheeler. As the tricycle picks up speed, the rear wheels get closer together, until they merge into a single wheel.