Abstract: A sorting apparatus and method for fractionating and simultaneously viewing individual microstructures, such as free cells, viruses, macromolecules, or minute particles in a fluid medium. The sorting apparatus is composed of a substrate having a receptacle located therein, the receptacle having sidewalls and a floor. An array of obstacles is positioned within the receptacle with the obstacles upstanding from the floor of the receptacle. A transparent cover overlies the array of obstacles to cover the receptacle and afford visual observation of migration of the microstructures exclusively through the array of obstacles. Electrodes may be positioned within the receptacle to generate an electric field in the fluid medium in the receptacle in order to induce the migration of the microstructures. Migration of the microstructures may also occur, for example, by a hydrodynamic field, an optical field, a magnetic field, or a gravity field applied to the receptacle.