Determining CCS growth rate distributions. (A) Fluorescence intensity trace of a clathrin hotspot imaged at the ventral surface of a BSC-1 cell expressing AP2-GFP. Traces segments that are not used in growth rate calculation are shown in red, as they were considered the background signal. (B) Zoomed version of the clathrin-coated pit trace marked by the arrow in A. Shaded regions show 12-s-long fragments dwelling at formation (red), plateau (green), and dissolution (purple) phases of the pit. (C, left) For the intensity trace in A, slope values representing the growth rates are determined from 12-s-long fragments centered on each time point. Red, green, and purple arrowheads mark the slopes corresponding to the growth, plateau, and dissolution fragments highlighted in B, respectively. (C, right) Bar plot shows the distribution of the growth rates shown in the left panel. Positive and negative values correspond to formation and dissolution phases, respectively.