Did you ever wonder how we can date and authenticate a glass window? Onside of art historical studies, scientific methods can be applied. To retrieve the dating and origin of glassworks, completely non-destructive analyses are required. Photonics, the science of light, emerged as a key enabling technology in this field. Light behaviour (absorption, transmission and reflection) depends on the material. Our PhD researcher Mathilde Patin is using these light properties to study glass windows from the 15th c. to the 17th c. in the frame of her PhD, inserted in the FENESTRA project. She explains in a video for Science Figured Out (Wetenschap uitgedokterd).