Number and identity of metabolites obtained with intact biopsy method and the standard ground tissue extraction method. The total number of metabolites detected using each sampling and extraction protocol (30 mg tissue, intact biopsy, ground biopsy) is shown in the rectangles at the bottom of the figure. The Venn diagram represents the overlap in the identity of metabolites detected using each method. The vast majority (266) of metabolites are detected using all three methods. Metabolites were extracted from intact biopsies with 80% methanol.