From about 1544, many maps were produced, especially in the important trading centers of Rome and Venice. Each publisher worked independently. They produced maps based upon their own needs. The maps often varied dramatically in size. Over time, it became common to bind the maps together into one book. Although the term atlas was not in use in 1544, these works are now called "IATO" atlases - (Italian, Assembled to Order) or more frequently "Lafreri atlases" after one of the leading publishers of the period. 