English: NanoSIMS analysis of a diatom and bacteria (white arrow) provided with stable isotope labeled 15N nitrate. In panels 1-e, dark blue represents low counts of each isotope, and yellow is high counts. The bacteria, but not the diatom, incorporated the heavy 15N, as seen in panel c. The natural 15N to 14N ratio is 0.04. Any ratio above this indicates the organism incorporated the 15N nitrate into their organic matter. The natural differences in 32S abundance between the bacteria and diatom can also be seen (panel d), along with the 28Si signal of the frustule of the diatom, made of silica (panel e). Panel f is a fluorescence of the same diatom. The red box indicates the same view seen in panels a-e. Each nanoSIMS image is 50 um by 50 um. Image provided by the International Geobiology Training Course and Orphan Lab, Caltech.