In the 13th century BC, the earliest windows were unglazed openings in a roof to admit light during the day. Later, windows were covered with animal hide, cloth or wood. Shutters that could be opened or closed came next. Over time, windows were built that both protected the inhabitants from the elements and transmitted light, using multiple small pieces of translucent material, such as flattened pieces of horn or thin slices of marble, set in frameworks of wood, iron or lead. In the Far East, paper was used to fill windows. The Romans were the first known to use glass for windows, a technology likely first produced in Roman Egypt, namely in Alexandria ca, 100 AD. Cast glass windows, albeit with poor optical properties, began to appear, but these were small thick productions, little more than blown glass jars (cylindrical shapes) flattened out into sheets with circular striation patterns throughout. It would be over a millennium before a window glass became transparent enough to see through clearly, as we think of it now. Today, we are spoilt for choice when it comes to size, shape, configuration and glass type.