Modern brain scanning techniques like functional MRI generate voxels, or 3-dimensional cubes, sized approximately 1 cubic millimeter per voxel. To describe human brain requires over 1 million voxels. To see all synapses in a single voxel it is necessary to generate 2,000 terabytes of data, or 2 petabytes per cubic millimeter. That equates to 2 million petabytes of data for a single brain which is comparable to all digital content of the world in 2014.
Number of voxels could be increased to 12 million with Diffusion Tensor Imaging.