Time-lapse measurements were also performed with a 100 nM α-Syn solution. AFM images for 2, 3 and 5 hours of continuous observation, shown in Supplementary Fig. 5, clearly illustrate the time-dependent aggregation of α-Syn. Similar to the previous experiments, the surface was imaged first in 10 mM sodium phosphate buffer (pH 7.4) to confirm that the surface was clean (Supplementary Fig. 5A(i)). Then 100 nM α-Syn was injected onto the surface, and imaging was continued. A considerable number of aggregates were observed after 2 h (Supplementary Fig. 5A(ii)). The number of aggregates was further increased at the 3 and 5 h time points. (Supplementary Fig. 5A(iii, iv)). The volume distribution of the aggregates indicates that the size of the aggregates increases with time (Supplementary Fig. 5B). Similar time-lapse experiments with 10 nM α-Syn demonstrating the surface induced aggregation has also been performed and the data are shown in Supplementary Fig. 6. Apart from globular aggregates, the formation and growth of fibrillar features was also visualized (Supplementary Fig. 6B). In this dataset, an initially small fibrillar complex was observed in plate (i) and found to grow in size over time (plate (ii) and (iii)), but became smaller later on (plate (iv)). This set indicates that the assembled complex is not stable and can dissociate. A control experiment in connection with all of the time-lapse studies mentioned above was performed by imaging a mica surface in 10 mM sodium phosphate buffer (pH 7.4) without any protein for an extended period of time (up to 6 h) (Supplementary Fig. 7). This experiment did not show the appearance of any aggregate like features even after 6 h.