There were two main techniques in Greco-Roman mosaic: opus vermiculatum used tiny tesserae, typically cubes of 4 millimeters or less, and was produced in workshops in relatively small panels which were transported to the site glued to some temporary support. The tiny tesserae allowed <answer>very fine detail</answer>, and an approach to the illusionism of painting. Often small panels called emblemata were inserted into walls or as the highlights of larger floor-mosaics in coarser work. The normal technique was opus tessellatum, using larger tesserae, which was laid on site. There was a distinct native Italian style using black on a white background, which was no doubt cheaper than fully coloured work.
What was the benefit of using small pieces to create a mosaic?
very fine detail