Current techniques available for imaging of alpha particles, such as alpha autoradiography, are only able to produce planar (2D) images of 3D tissue samples containing radioactive substances. We introduce a new imaging technique, which we call Alpha Emission Tomography (αET), for the reconstruction of the volumetric (3D) distribution of radiotracers that emits alpha particles. Our imaging system is able to measure position and energy of each detected alpha particle. The list of measured positions and energies is fed to an iterative algorithm for 3D reconstruction. We predict that αET will become a valuable imaging technique for molecular biology.