"Resconstruction of the solar corona in 3D with STEREO" ------------------------------------------------------- Our aim is a 3D-reconstruction of the coronal magnetic field and plasma. Unfortunately we usually cannot measure the magnetic field and plasma density in the corona directly. To get insights regarding the structure of the corona we combine measurements from the two STEREO-spacecraft with photospheric magnetic field measurements, e.g. from Hinode. A nonlinear force-free extrapolation of the photospheric magnetic field vector into the corona provides us the coronal magnetic field. We developed a stereoscopy and tomography tool for the 3D reconstruction of the coronal plasma from two viewpoints, as provided by STEREO. Both tools make use of the force-free coronal magnetic field model, which allows to remove well known ambiguities in traditional stereoscopy and tomography. In the advent of STEREO and Hinode we tested our tools with model configurations and data from SOHO, TRACE and ground- based observations.