Figure 1.

a, Three-dimensional drawing of the resin block showing the arrangement of the gallium ion beam (white) that scans parallel to the block (indicated by double-headed arrow) and mills away a layer of resin, creating an imaging face. The electron imaging beam (gray) at an angle of 52° from this vertical face is then used to image the embedded tissue at this surface. b, Scanning electron micrograph of a tissue block in the same orientation as a with a dotted line indicating the milled region, which is shown in c in reverse contrast. Scale bar, 20 μm.