With tomographic in situ visualization we present a novel approach to interactive data visualization and exploration. This visualization concept is useful for presentation of spatially co-located information that is normally not visible to the human's eye. The tomographic in situ display allows for interactive cutting through data in space by using a spatially tracked and calibrated display. In this paper we describe the technical apparatus of our prototype and describe an application for the tomographic in situ visualization in the field of indoor climate studies.