文档介绍：Most cells are transparent—in other words, they are not very good at reflecting or absorbing light. To look at them under a microscope thus requires trickery. Many of these tricks kill the cells, and even those that keep them alive look only at slices through each cell, rather than seeing the whole thing in three dimensions.
Michael Feld, of the Massachusetts Institute of Technology, and his colleagues, think they can change that. They have invented a way to look at cells that are still alive. Moreover, they can do so in three dimensions. Their method is called tomographic phase microscopy, and it is reported in this week's Nature Methods. Instead of relying on absorbed or reflected light, Dr Feld's technique celebrates transparency by looking at light that gets through unaltered. It does so by measuring a property called the refractive index.
This index measures the speed of light in a material. (Light zips along at the actual “speed of light”, faster than which nothing can go, only when it is travelling through a vacuum.) The ponents of a cell, though transparent, have different refractive indices. Dr Feld and his team therefore set out to map what these differences are, with a view to using them to distinguish between ponents.
To measure the refractive indices of different parts of a cell they use a technique called interferometry, which involves splitting a beam of li