The LEAP 4000X is a three-dimensional atom probe microscope which provides nano-scale surface, bulk and interfacial materials analysis of structures with atom-by-atom identification and spatial positioning. The technique is based upon the principle of field evaporation, where a strong electric field is sufficient to cause the removal of atoms by ionization from a very sharp tip. Repetition of a pulsed voltage or laser progressively removes atoms from the apex of the specimen one-by-one. The atoms leaving the specimen surface are detected by a position-sensitive imaging mass spectrometer and recorded. The time-series data-set collected is reconstructed into an atomic scale 3-dimensional model or tomograph of the specimen Specimens are typically in the form of micrometer long needle shaped object with a tip diameter less than about 200 nm and a radius of curvature of about 100 nm. Specimen preparation often includes electropolishing for metals or FIB milling for any solid bulk specimen.