The disclosed technology relates to a method and apparatus for atomic probe tomography (APT). The APT relates to the 3-dimensional reconstruction of the material of a sample having a free-standing tip, wherein an image is repeatedly obtained of the tip area through ptychography or ankylography, in the course of the APT analysis. In one aspect, imaging of the tip is achieved by directing a coherent light beam in the soft X-ray energy range at the tip during the APT analysis. The photons of the X-ray beam are not affected by the strong electric field around the tip, and thereby allow to determine the image of the tip through the application of a ptychography or ankylography algorithm to the data obtained from a photon detector. The photon detector is positioned to detect interference patterns created by photons which have interacted with the tip area, at different overlapping spots of the tip area, when the X-ray beam is scanned across a plurality of such overlapping areas. The method and apparatus allows real-time monitoring of the tip shape, as well as the feedback of the recorded tip shape in order to take tip deformations into account in the APT analysis.