In 1999 Sunney Xie and coworkers at Pacific Northwest National Laboratory published an article containing an image of three cervical cancer cells, in which each cell’s mitochondria appear as bright yellow splotches in a sea of red cytoplasm.1 The researchers used no fluorescent labels or stains to generate the color contrast; rather, they used a technique known as coherent anti-Stokes Raman scattering (CARS) microscopy.

The technique was developed in the early 1980s at the US Naval Research Laboratory, but it went virtually unnoticed until Xie and colleagues rediscovered and refined it. In the past decade, CARS has stirred considerable interest among biologists, and now work by Robert Burruss (US Geological Survey), Aaron Slepkov (Trent University, Peterborough, Ontario), Albert Stolow, and Adrian Pegoraro (both at National Research Council Canada) suggests the technique could also prove useful to geoscientists.2 Applied to translucent samples of sedimentary rock, CARS microscopy produced richly...

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