AbstractThere are a limited number of phenomena occuring with aerosol particles that depend only on physical quantities. Examples of new developments in aerosol particle characterization in situ that make use of such phenomena are briefly reviewed. They concern electrophoretic size classification, inertial size analysis and shape characterization of agglomerates. In addition to deriving basic descriptors, measurements of composite quantities can be performed and developed into sensors. Examples of sensors responding to relevant complex aerosol quantities are explained.