Particle engineering in pharmaceuticals has evolved from conventional granulation and milling techniques to advanced techniques like supercritical ¢uid technology, jet milling, spray drying, high pressure homogenization, spray congealing, extrusion-spheronization, spherical crystallization, and crystallo-co-agglomeration. This engineering of solids has been aimed to alter and improve the primary physical properties of solids such as particle size, shape, crystal habit, crystal form, density, porosity, etc. as well as secondary properties like ¢owability, compressibility, compactibility, consolidation, dust generation, and air entrapment during processing. In the pharmaceutical industry, ef›cient production of small and/or substantially uniform particles is desired not only due to its impact on performance during processing and storage but also due to its impact after consumption by patients. Micronization of drugs is routinely carried out for increasing dissolution rate. Currently, nanosized particles are explored due to advancement in techniques available for nanoparticle formation. For inhalation drug delivery system, the particle size, shape, and surface properties determine its interaction with the container and amount of dose deposited in lungs, which is generally the desired site of action.