Professor Jeff Lichtman introduces fluorescence microscopy, a powerful technique of illuminating minuscule molecules for analysis by very powerful microscopes.

There are many different ways one can image the brain and one of the most exciting is a method known as fluorescence microscopy. Fluorescence microscopy is a complicated term for really a very simple idea, which is that there are molecules that are made by people, and also molecules that show up in nature in which you can get them to give off light if you shine light on them of a different color. Some people may remember the good old days when people my age were in college, and in our dormitories we would have these posters on the wall and we would shine what is called a black light which is actually ultraviolet purple light that is very hard to see, on to these posters and these very bright colors like yellow, blue, and green would come out very bright even though we weren’t shining those colors on to these posters. And what that was occurring because of is the pigments in the posters were fluorescent. So if you shine a high energy light like ultraviolet light, on to a poster, these pigments then give off their native colors which is yellow, red, or blue in this intense color in a background that is quite dark. And it is exactly this idea that makes fluorescent microscopy a very powerful technique, because in a dark sample if cells or molecules inside the nervous system are tagged in a way that they are fluorescent then if you shine light of the right color on them they will bring out these very bright colors on a very dark background so you can see minuscule amounts of molecules or the structure of very small cells.

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