In the above, we have seen that spatio-temporal proximity effects in parallel writing appear to be caused or reinforced by different factors: small inter-spot distance of the DOE generated write spot array, low numerical aperture of the objective and chemical nature of the photoresist (monomer mixture). All these parameters have in common that they render the polymerization threshold in the vicinity of the exposed areas more sensitive to radical diffusion effects. Moreover, at very short (sub-micron) inter-voxel distances, other optical effects, conceptually related to the well-known Talbot effect, also appear to come into play and hamper parallel writing.