To quantitatively characterize the aggregation process, we measured the aggregate volume and number at all incubation times, and the data are shown in Fig. 1D and Supplementary Fig. 1. The distribution of aggregate volumes is approximated with a single Gaussian for the 24 h incubation with a maximum of 107.2 nm3 (Supplementary Fig. 1A), but the distributions are bimodal for two longer aggregation times (48 h (Supplementary Fig. 1B) and 72 h (Supplementary Fig. 1C)), indicating the formation of two sets of aggregates. The sizes of aggregates that appear after a 72 h incubation in the bulk solution were also measured, and the distribution is shown in Supplementary Fig. 1D. The overall number of counts is low due to a low yield of globular aggregates, and their sizes are more than 50 times smaller than those found for the aggregates formed on the surface. Thus, interaction with the surface dramatically enhances the Aβ-42 aggregation process.