Por vezes, eram cortadas em dimensoes ainda mais reduzidas (3 ou 4 mm quadrados) e justapostas para formar uma variante do opus tessellatum: o
opus vermiculatum, cujo nome deriva de vermiculus (verme, em latim), devido as minusculas tesselas que o compunham.
Michael Hedqvist of Phoenix Ancient Art confirms this view: 'Mosaic making reached a pinnacle in 1st-century Rome, with a technique known as
opus vermiculatum or micromosaic.' While Antioch in Turkey was a major centre of mosaic art, he suggests that 'the best examples of such production are found in Rome and Naples [from Pompei].
The mosaic is made with minute glass tesserae (none larger than 0.25 cm, in many parts of the figures smaller than 1 mm square) in
opus vermiculatum (worm-like), a technique in which one or more rows of tesserae curve around the figures, emphasizing them and foreground elements in a halo effect.