In this June 22, 2016 photo, Don Holman, an engineer at the U.S. Army Natick Soldier Research, Development and Engineering Center in Natick, Mass., adjusts a vertical rack under LED grow lights as kale and other lettuces sprout inside a refurbished shipping container. Holman is testing the idea of growing vegetables hydroponically in a shipping container that could be put on board a submarine to provide fresh vegetables to sailors. (AP Photo/Elise Amendola)