Single cell endogenous and xenobiotic metabolite detection using nanostructure-initiator mass spectrometry (NIMS). NIMS total ion intensity (panel A, left), glucose ion intensity (center) and uridine ion intensity (right) of 3′-deoxy-3′-fluorothymidine (FLT)-treated Raji cells. The total-ion NIMS image indicates that numerous cells are present in the same regions on the NIMS surface as suggested by high-intensity localized signals. (B) Typical NIMS mass spectra observed from a pixel corresponding to a putative single cell in the NIMS Raji cell images. Left panel, FLT peak [M-H] 243.08 m/z) from a single cell; center, FLT-MP [M-H]323.05 m/z) peak from a single cell; right, single-pixel NIMS spectrum across the 75 to 650 m/z range.