Modern facades, whether made of glass or including transparent, translucent or reflective elements, let through a particular light spectrum or change its intensity in many different ways. “Filtering facades” may change the image seen through them or change the colour of passing light according to specific circumstances: the angle of observation or temperature. These indicated properties of facades acting as “filters” were made possible due to the great technological development observed in the last two to three decades, though the general characteristic of this phenomenon of optical filters had already been explored since the XVII century by Newton, and later on by Fresnel, Fraunhofer, Maxwell and Planck. Thanks to material engineering today it is possible to create unique glass facades with great functional properties, yet architects, engineers and artists do not stop at this point. The experiments undertaken in these fields explore transparency, reflection, refraction and diffusion and lead to fascinating effects that are worth examination.