The mosaic-makers had to be and had to be ready for work, which is why they also speak of mosaic artists or mosaicists. From small mosaic stones with an edge length of 1-2 cm or smaller, pictures and ornaments up to several meters in size were or will be created. Tesserae are rarely made of stones or semi-precious stones, mostly of glazed stoneware, porcelain or colored cast glass. In contrast, when the tiler speaks of mosaic, he means small-sized tiles between 50 x 50 and 100 x 100 mm. The mosaic stones are laid stone by stone in a mortar bed after a preliminary drawing, grouted and smoothed if necessary. In newer techniques, the mosaic is placed in its entirety in the mortar bed. For this purpose, it must first be applied to a grid or mirrored on paper or foil. From when exactly there were mosaics, can not be estimated so accurately. For most historians, however, the history of the mosaic begins with the Greeks.