Unlike most sculptors, I am only sculpting the inside of my stones, never the outside. In the beginning (from September 2003) I made simple forms as balls, lenses, rings and cubes inside stones. One of my major principles is that the integrity of the stones may never be damaged outside. My work is strongly influenced by Escher, and lately also by one of the worlds leading sculptors Keizo Ushio. As the outside of the stones must remain as intact as possible, it is the end result that dictates the way of going into the stone. The working process of the making of the Hidden Split Torus 540 is explained. During the Biennale (1-9 December 2007) in Florence Italy this sculpture was the topic of a talk by art critic Paul Lorenz from the Art Academy of San Francisco.