Principal component analysis visualization of the 'metabolic phenotypes' of Columbia-0 wild type, C-24 wild type, and the corresponding cross (F1 generation). Plants grown under controlled environmental conditions were harvested at the same developmental stage. Eight pools, each containing eight plants, were extracted and analyzed by 'metabolite profiling' (for protocols, see http://www.mpimp-golm.mpg.de/fiehn/index-e.html). GC/MS was used to automatically quantify 500 metabolites. Principal components analysis (which uses an n-dimensional vector approach) was undertaken to summarize metabolic profiles covering 500 metabolites. After application of PCA algorithms, vectors 1, 2 and 3 were chosen to best represent the distinct metabolic profiles associated with each genotype. Each point in the parental lines represents a linear combination of all the metabolites from an individual sample. Courtesy of Oliver Fiehn, with acknowledgements to Thomas Altmann and Bernd Essigmann for contributions to the experimental design.