This is a Scanning Electron Microscope image of a marble surface on which a protective coating of apatite was deposited. As acid rain causes the dissolution of calcareous stones such as marble, the protection of buildings, monuments and sculptures from environmental degradation is of fundamental importance, both to preserve our cultural heritage from destruction and to save energy otherwise required for conservation and restoration work. A surface-protective treatment aimed at forming a “forest” of apatite crystals -- more resistant than marble to acid attack -- is therefore currently under investigation in our art conservation laboratory.