The huge circular stained glass windows seen in Gothic churches are known as rose windows. They were inspired by the oculus, a tiny, spherical window used in ancient Roman construction. The word "rose" in English may also be used to describe any small, circular window. The term "rose window" first appeared in the 14th century when stained glass artists began to use it to describe one of several large windows they would have shipped with their merchandise. These windows would have been sold separately from the stained glass panels that made up the rest of the church window. The merchant who bought these windows would then install them in his building as decorative art. By the 15th century, roses were becoming larger and more elaborate. They were now being used not only as decorative elements but as scenes from the Bible or other religious topics. These windows served as valuable sources of income for poor priests who didn't own land or money enough to afford expensive paintings on wood or canvas. In the 16th century, under the influence of humanism and classical culture, roses started to look less like flowers and more like sculptures. Designers even began to embed iron rods inside the glass to allow them to bend and model the forms they wanted to portray.