The World Health Organization warns that overpopulation and a lack of arable land contribute to global food insecurity. So scientists are developing new farming technology to offset potential food shortages. Researchers in South Korea are experimenting with vertical farms; gardens that go straight up, instead of spreading out.

Agriculture in high-rise buildings is the dream of some scientists and architects around the globe. But it soon could be reality.

Just outside of Suwon, a city 30-kilometers south of the capital Seoul, the South Korean government is experimenting with urban agriculture. The Rural Development Administration has built a prototype of a vertical farm.

So far, their experiment is only three-stories high. But they hope that in the near future, the technology will expand and be capable of feeding the entire nation.

Their work is inspired by Dickson Despommier, the scientist credited with inventing the idea of vertical farming.

Despommier says tower-like hydroponic farms could someday stand alongside skyscrapers as a key food source for billions of city dwellers. He sees them as a key solution for growing populations with limited arable land.

"Here's my vision of what a vertical farm might look like. My gold standard for this is the Apple Store in New York City on 5th Avenue," said Despommier. "If you took that building and made it into a five-story building. Now in the building you have multiple floors, of course, and inside each floor you have multiple layers of crops."

Back in the Suwon lab, agrarian scientist Choi Kyu-hong is still sorting some basic challenges.

"The plant factory requires a lot of energy, the light energy and the heating and cooling energy. So we provide the heating or cooling energy using geothermal systems. We adopted the solar-cell system to provide light source energies, but we are still [only] providing 15 percent of the total energy," said Choi.

Choi said there are other challenges to overcome before the farms become a viable alternative food source. Scientists are determining the optimum light wavelength for growing each kind of plant.

Team member Lee Hye-Jin said they need more time.

"It might take at least five more years of research to make progress on these obstacles. Then vertical farms might be ready for commercial use," she said.

The South Korean scientists say that once these problems are resolved, vertical farms won't just have to stop at three-stories. The sky is the limit.