When it comes to plants, the roots hidden underground are as important—if not more—than what’s visible above ground. Now, researchers have figured out how roots from different plants divide up the space between them. Because roots hidden in soil are hard to monitor, researchers first developed a mathematical model that predicted how roots might grow with and without competition from an adjacent plant. Then they tested their predictions by growing pepper plants alone or with a neighbor. To see what the roots did, they injected red dye into one plant and blue dye into the other and checked root distributions in the soil around them. As this video shows, a plant on its own will sprout ever more roots around its base while at the same time extending its reach underground in all directions. But with another plant nearby, it shifts root production to focus more on roots nearby, and avoids overlap with its competition, maximizing how many nutrients it gets, the researchers reported in Science.