Distribution of ssDNA in grid holes upon vitrification. (a) Transmission electron micrograph of an ssDNA-coated grid vitrified without macromolecular sample. The carbon edge and entangled strands of ssDNA are indicated with white and cyan arrows, respectively. (b, c) The insets show details of the entangled ssDNA strands at different distances from the carbon edge. The white scale bar represents 100 nm.