Image: W.Min / S.Lu of Harvard University
THE MOMENT: Blood vessels (red) and the surrounding glands (green) come to life in this image of the microvasculature network inside a mouse ear. The red in the image comes from stimulated emission microscopy (SEM) of hemoglobin in red blood cells, which has been overlaid on a image of sebaceous glands captured using transmitted light.
THE SHOT: The micrograph comes from a study in the latest edition of Nature in which scientists show how stimulated emission—the same technique used to amplify light in lasers—allows them to highlight molecules that are usually hidden in the dark. Normally, to see inside cells or tissues scientists look at fluorophores, which are special molecules that do not respond to light by giving off heat, but rather—after some wiggling—relax by emitting a lower-energy photon, which is readily visible. However, not all molecules are fluorescent, and to tag something with a fluorophore requires some tinkering—not ideal for looking inside living cells or tissues. SEM works by first exciting the molecule of interest (in this case hemoglobin) with light, and then hitting it with a second light of slightly lower energy. This causes the excited molecule to relax by emitting a photon that is an exact copy of the second light source.
