To better evaluate which fingerprints provide different views of the NP chemical space, we calculated the Pearson correlation coefficient between each pairwise similarity score across all fingerprints (Figure ). It is immediately apparent that both pharmacological fingerprints (PH2 and PH3) are outliers, given that they are extremely correlated between each other and almost completely uncorrelated with all others. This could be related to the fact that, unlike the other fingerprints analyzed, these fingerprints describe the occurrence of 'fuzzy' pharmacophoric points, rather than focusing on the presence or occurrence of functional groups and substructures.