One atom casts a shadow

Seems unlikely that you could record the shadow of just one atom — but you can, appar­ently, if you use the right fre­quency of light. Get it wrong by one part in a bil­lion, though, and the shadow van­ishes. This isn’t just a curi­os­ity — this sort of study should help determ­ine the optimum con­di­tions for micro­scopy, so you can use as much light as pos­sible to observe cel­lu­lar pro­cesses without des­troy­ing the cell. Read more here.