Histology of hematoxylin and eosin (H & E) stained sections from the abdomen of a healthy uninfected adult zebrafish (a) and a diseased adult zebrafish infected by M. marinum (b), showing severe granulomatous infection. The granulomas are visible in the H & E stain image as lighter structures with clearly visible cores which are indicated with small white arrows. TOF-SIMS (MS¹) total ion current (TIC) images, acquired in the positive ion polarity, of healthy (c) and diseased (d) zebrafish tissue sections. The sections used for MS imaging analysis were consecutive sections adjacent to those used for histology. The major organ groups are identified. TOF-SIMS (MS¹) images of healthy (e) and diseased (f) zebrafish tissue sections produced from positive polarity ions at m/z 430 which were identified by tandem MS (MS²) imaging as α-tocopherol. The green box in panel (f) indicates the approximate location of the tandem MS analysis for identification of the m/z 430 precursor ions