Vertical farming is a form of agriculture that grows plants indoors in floor-to-ceiling on tower-like walls of plant-holding cells. In place of sunlight these plants grow under LED lights in temperature controlled indoor environments that leverage cutting-edge technology. Crops grown in a vertical farm facility do not need soil as typically their roots are held in a cell lining composed of fiber.

Initially proposed by professor Dickson Despommier (of  Columbia University) as a theoretical construct, modern vertical farming is rapidly growing into a serious business driven by technological innovation and changing societal concerns. Expect continued rapid change in this sector as the market matures with the technology and with societal needs. Some helpful resources:

This PBS Sponsored video is a great primer