This review includes the most recent advances in fine particle characterization based on direct and indirect methods. Fine particles characterized with the size of 2.5 micrometer are defined as particles that have reduced visibility to the human eye, and causes the air to appear hazy when levels are elevated. Within this article, pharmaceutical drug formulation of fine particle size and distribution is well defined as described by the United States Pharmacopeia (USP). This review highlights the direct methods, which include the following: sedimentation rate, analytical sieve fractionation studies, and light microscopy; as well as indirect methods of characterization, which includes laser diffraction analysis, method validation and permeability procedures. Furthermore, statistical analysis in particle size is expressed within and it is used to summarize large amounts of collected data into a form that could be useable and understandable while losing as little information as possible about the original investigated population.