Important information about an aerosol resides in the morphology (size, shape) and in the chemical composition of individual particles. To get this information, the existing, well-developed modern methods of single particle analysis are the most useful methodology. 1 , 2 In some cases (e.g., in the measurement and identification of fibrous aerosols), the methodology of single particle analysis is the methodology of choice. The anthropogenic fibrous aerosol existing in the working, indoor, and outdoor environments is always mixed with other types of aerosols and dusts. It is necessary to have methods that are able to differentiate between fibrous and nonfibrous (isometric, spherical) particles. The best way is to be in position to “see” directly (microscopical methods) the shape of individual particles or to detect the particle indirectly, e.g., by means of light scattering methods. Some other important aspects of such measurement are the biological effects of inhaled fibrous particles. These health effects are related to the particle shape and size and to several chemical markers of single particles (solubility, elemental composition, fiber surface activities, etc.). A combination of electron microscopical methods with single particle analysis is an optimal solution for the measurement and identification of fibrous aerosols. Fibrous dusts and aerosols consisting of asbestos and natural or man-made mineral vitreous fibers (MMVF), whether dispersed in workplace environments or the indoor and outdoor atmosphere, are toxic, fibrogenic, and carcinogenic. 3 , 4 Their measurement in air, personal dosimetry, and in some instances, real-time monitoring is necessary. Airborne asbestos is, therefore, a special case of fibrous aerosols. While asbestos fibers have many useful commercial and technological properties, there has been much concern regarding their ability to cause disease. There are three primary diseases that have been attributed to asbestos fiber exposure: asbestosis, mesothelioma, and lung cancer.