Complex sentence: Oak galls have been used in the production of ink since at least the time of the Roman Empire; from the Middle Ages to the early twentieth century iron gall ink was the main medium used for writing in the western world.
Split into simpler sentences: Oak galls have been used in the production of ink since at least the time of the Roman Empire. From the Middle Ages to the early twentieth century iron gall ink was the main medium used for writing in the western world.