Fig. 4

Determination of the correct oil before the first scan. a1–5 Preview images of the first focal point of grid-free signals (a1), the first occurrence of the grid on the specimen (a2), the mid-section (a3), the last occurrence of the grid (a4) and the second focal point of grid-free signals. b1–5 show the same images as in (a1–5) with optimized contrast for improved visualization of the grid. c1 Orthogonal view of the first of the three non-reconstructed scans with different angles. The dashed lines mark sections (a1–a5). c2 Orthogonal view of the second of three non-reconstructed scans. Note the reduction of signal strength between the two scans caused by bleaching. d1 Orthogonal view of the reconstructed scan. The central dashed line marks the section of D2. d2 Reconstructed mid-section with full resolution