Just imagine, you are sitting on a sunny beach, contentedly letting the warm sand trickle through your fingers. Millions of sand grains. What you probably can't imagine: at the same time, billions upon billions of bacteria are also trickling through your fingers. Between 10,000 and 100,000 microorganisms live on each single grain of sand, as revealed in a new study. This means that an individual grain of sand can have twice as many residents as, say, the city of Fairbanks, Alaska!