There are 10^18 voxels in that cubic mm, so a petabyte (10^15 bytes) is not too bad. Must be a lot of empty space in there. Put another way: this is pretty cl

There are 10^18 voxels in that cubic mm, so a petabyte (10^15 bytes) is not too bad. Must be a lot of empty space in there. Put another way: this is pretty close to a football-field-sized cube, filled with sand. Each grain of sand is a voxel. The central bodies (soma) of neurons are about a yard wide at that scale.