Historians believe that cultures as far back as the ancient Egyptians had begun to experiment with the technology of creating and colouring glass. Now they certainly weren't making huge windows, but they were starting to experiment with small scale glass production, creating jewels and beads for ornamentation and for religious purposes. Certainly it would only have been the richest and most powerful for who would have access to the glass creators skills. After all the creation of such a material as glass would probably have been seen as a magical, alchemical process. The Kings and Queens who would won the glass jeweled ornamentations would no doubt have used their possession to reinforce their image as the all powerful ones.
Here we can see two distinct forms of stained glass window, found within the same Cathedral. Both these images were taken in Liverpool Cathedral.
The one on the left shows a fairly modern style of semi abstract geometric imagery. Whilst the one on the right shows a much more traditional form of stained glass, more clearly figurative and incorporating some painting on the glass where details such as faces are required.