Apart from the use of synthetic materials such as fibreglass and polyester, and mechanical systems for opening and closing them (how lazy can we get?) Curtains have not really changed all that much for thousands of years! There is evidence that they were used as room dividers (called portieres) in ancient Pompeii and Herculaneum, and back in the Middle Ages heavy cloth drapes were hung over window openings in place of shutters and beds had curtains all round them to stop the occupants from freezing in the icy draughts that was the blow through most homes of the era.
As people became more affluent windows were glazed and curtain materials improved from rough homemade cloth to woven woollens and in Italy there is evidence that even velvets and down mask were used. During the Renaissance artistic forms of curtaining were used which were even richer than any normally seen today, with braiding, rich tassles and ribboning adding to their complex designs. During the 19th century in wealthy British households the focus switched to pelmets and finials in highly decorative carved wood with designs such as birds, flowers and Greek themes. During the Victorian era the designs were extremely heavy and pretty well everything that could be curtained was curtained with doors and windows covered with thick but fine material in scrolled or large floral patterns.
It is now possible to buy either curtain material already made up curtains in virtually any material, pattern or colour online from specialist stockists who in most cases will be able to give you a better choice as well as lower prices than the majority of retail stockists.