Want to see where your food might come from in the future? Look up.

The seeds of an agricultural revolution are taking root in cities around the world—a movement that boosters say will change the way that urbanites get their produce and solve some of the world's biggest environmental problems along the way.

It's called vertical farming, and it's based on one simple principle: Instead of trucking food from farms into cities, grow it as close to home as possible—in urban greenhouses that stretch upward instead of sprawling outward.

The idea is flowering in many forms. There's the 12-story triangular building going up in Sweden, where plants will travel on tracks from the top floor to the bottom to take advantage of sunlight and make harvesting easier. Then there's the onetime meatpacking plant in Chicago where vegetables are grown on floating rafts, nourished by waste from nearby fish tanks. And the farms dotted across the U.S. that hang their crops in the air, spraying the roots with nutrients, so they don't have to bring in soil or water tanks for the plants.

However vertical farming is implemented, advocates say the immediate benefits will be easy to see. There won't be as many delivery trucks guzzling fuel and belching out exhaust, and city dwellers will get easier access to fresh, healthy food.