Throughout the twentieth century, the glass object ceased to be a mere exercise in technical virtuosity, transforming instead into a tool for philosophical and formal inquiry. This lecture explores how the transparency and fragility of glass were interpreted by the great masters of the twentieth century. Starting with the cubist deconstructions of Pablo Picasso—where the glass becomes a dovetailing of planes and volumes that challenge traditional perception—the journey arrives at the silent metaphysics of Giorgio Morandi. In his still lifes, bottles and glass vases lose their material consistency to become pure light, rhythm, and interior space. Through the analysis of selected masterpieces, we will observe how glass has been used to narrate modernity.