Farms may be going the way of the skyscraper, expanding upwards rather than outwards as land becomes more and more limited. Though the term vertical farm was first introduced by Gilbert Ellis Bailey in 1915, agricultural has remained a mostly horizontal affair until recently. Now, Singapore and Memphis are among a growing number of cities discovering the possibilities of looking to the sky for farm space.

Rows of 30-foot tall packed with rotating shelves that look like a Ferris wheel are neatly lined in Singapore’s first commercial vertical farm, Sky Greens. The brainchild of local entrepreneur Jack Ng now provides local grocery stores with produce like bok choy and Chinese cabbages. In Memphis, a collective known as Green Girl Produce will build the city’s first indoor vertical farm as a solution to combat a lack of fresh produce within close proximity. Their goal is to introduce Memphis to “indoor vertical farming, microgreen production, and a restaurant cooperative.”

The solution is not always the right way to go, says Gene Giacomelli who directs the Controlled Environment Agriculture Center at University of Arizona. When it comes to dense American cities like New York and Chicago, limited access to direct sunlight mean vertical farms would be less effective than rooftop greenhouses.

According to a 2011 report by the United Nations, the U.S. is among five countries to witness the biggest increase in urban population, adding 103 million people in 40 years. Vertical farms are just one way to help keep the food supply up to speed with growing demand.