The 1996 Nobel Prizewinner gives this years Nature Lecture. Chemistry is the art of creating compounds, and a fundamental of understanding requires an awareness of the structure of molecules on the scale of atoms. This scale is the nonometer scale, in which dimensions are of the order of a millionth of a millimeter. When we look at compounds they just appear like liquids or solids. Sometimes the crystals look beautiful, but in general, one liquid looks muck like another. However, the chemist who creates these materials can see in his mind the structure of the individual molecules and understand their beauty. Is it really an architectural awareness of molecules of this scale, and the drive towards creating new compounds is often no different from the creative urge which stimulates the artist or architect to create a new sculpture or building.