The Self-organizing map (SOM) is a popular (again) and intuitive non-linear mapping method: it transforms a multidimensional space into two dimensions (normally: they are so easy to visualize). Latino and Aires-de-Sousa published a paper that uses this method to analyze the whole KEGG pathway database: Genome-Scale Classification of Metabolic Reactions: A Chemoinformatics Approach (DOI: anie.200503833). The method is based on earlier