of objects; however the vertical heights cannot usually be calibrated, contrary to other methods such as photogrammetry. Other types of 3D SEM reconstruction Inverse reconstruction using electron-material interactive models Multi-Resolution reconstruction using single 2D File: High-quality 3D imaging may be an ultimate solution for revealing the complexities of any porous media, but acquiring them is costly and time-consuming. High-quality 2D SEM images, on the other hand, are widely available. Recently, a novel three-step, multiscale, multiresolution reconstruction method is presented that directly uses 2D images in order to develop 3D models. This method, based on a Shannon Entropy and conditional simulation, can be used for most of the available stationary materials and can build various stochastic 3D models just using a few thin sections. Ion-abrasion SEM (IA-SEM) is a method of nanoscale 3D imaging that uses a focused beam of gallium to repeatedly abrade the specimen surface 20 nanometres at a time. Each exposed surface is then scanned to compile a 3D image. Applications of 3D SEM One possible application is measuring the roughness of ice crystals. This method can combine variable-pressure environmental SEM and the 3D capabilities of the SEM to measure roughness on individual ice crystal facets, convert it into a computer model and run further statistical analysis on the model. Other measurements include fractal dimension, examining fracture surface of metals, characterization of materials, corrosion measurement, and dimensional measurements at the nano scale (step height, volume, angle, flatness, bearing ratio, coplanarity, etc.). SEM is also used by art conservationists to discern threats to paintings' surface stability due to aging, such as the formations of complexes of zinc ions with fatty acids. Forensic scientists use SEM to detect art forgeries. Gallery of SEM images The following are examples of images taken using an SEM. See also References External links General HowStuffWorks – How Scanning Electron Microscopes Work Learn to use an SEM – An online learning environment for people wanting to use an SEM. Provided by Microscopy Australia Virtual SEM – sparkler an interactive simulation of a scanning electron microscope (SEM) Multichannel color SEM imaging and with BSE DDC-SEM image examples Video on the scanning electron microscope, Karlsruhe University of Applied Sciences Animations and explanations on various types of microscopes including electron microscopes (Université Paris Sud) History Environmental Scanning Electron Microscope (ESEM) history Images Rippel Electron Microscope Facility Many dozens of (mostly biological) SEM images from Dartmouth College. Lanthanoid staining