Buying food in Singapore can get expensive. The tiny island-nation relies on 35 countries to import 90 percent of its food. One of the main reasons for this is land scarcity—at only 280 square miles with a population of 5.3 million people, Singapore has just about ran out of space. Importing so much food makes any country vulnerable to food shortages. Singapore is now looking at urban farming to curb its reliance on foreign food. Companies like ComCrop build extremely efficient aquaponics gardens on rooftops that use less water and produce 10 times more food than soil-based farming. And Sky Greens can put down roots for 8.6 acres of veggies in a 30-foot vertical farm that uses a hydraulic rotating mechanism to bring plant down to water then back up to the sun.