Many biological functions depend on the interaction of small organized groups of proteins.
Revealing the 3D organization of such macromolecules is indispensable in order to understand their function. In contrast to other indirect and comparative methods in molecular biology, direct 3D imaging methods are very appropriate to study the 3D organization in an unperturbed cellular context. Electron microscope based tomography is a 3D imaging technique aimed at visualizing and identifying molecular structures. The application of electron microscope tomography for imaging of cellular sections at ultrastructural or molecular levels of resolution requires the development of advanced methods for signal reconstruction, statistical signal estimation, as well as for data exploration and visualization. Electron tomographic reconstructions from biological specimen are extremely noisy.