(A–C) The histograms show the normalized distribution of azimuth ( = horizontal orientation) of keratin filament segments in single cells. Since the start and end points are interchangeable, the histogram is restricted to 180 degrees. The horizontal line represents the expected histogram levels, if all angles were equally distributed. (D–F) The histograms show the elevation ( = vertical orientation) of keratin filament segments. The horizontal line demarcates the expected histogram values, if elevation of keratin filament segments would be uniform. (G, H) Whisker box plots depicting the deviation of segment orientations from uniform unbiased distributions. The differences in azimuth (G) and elevation (H) were calculated for 10 MDCK, 10 HaCaT and 10 RPE cells. (I–L) The color-coded maps depict the azimuth of segments in entire cells (top; MDCK, left; HaCaT, middle; RPE, right) and selected regions of interest (boxed areas; bottom).