The Triobike.

Via Metaefficient:

"Straight out of the heart of Copenhagen, comes the Triobike, an innovative cargo bike, that can transform itself into a regular bike and a stroller. It’s no surprise that this bike comes form Copenhagen — the city is filled with urban bikers. With the Triobike, you can transport your kids to school in the cargo bike, then, instead of riding the cargo bike around all day you just pull out a front wheel from under the cargo bay, put it on the front forks. You can then ride a regular bike or use the cargo section as a stroller."