Extrusion is one of the most applied technologies for polymer processing. We use extrusion to create polymer nanocomposites for application in automotive, electrical and packaging industrial sectors. These nanostructured materials have advantages in comparison to traditional polymer materials. Mechanical properties, barrier and surface properties, electrical properties and flame retardancy will be improved. We show the determination of concentration, particle size, dispersion (degree of intercalation/exfoliation) and mechanical properties of polymer nanocomposites in the melt by Ultrasonic, Near Infrared spectroscopic and light extinction measurements during extrusion in real time. We correlated all in-line data with off-line rheological measurements, electron microscopy, Raman imaging and mechanical properties. The polymers used are polypropylene and polyamide 6 with different nanofillers (layered silicates) and nanoparticles. We studied the influence of different processing conditions on the morphology and on final product properties. So we could measure the nanostructure formation process in real time along the extruder on different measurement points by adaption of ultrasonic, near infrared, Raman and light extinction sensors at the end and at different positions along the extruder. It was possible to measure different dispersion states caused by different processing conditions. We could describe the nanostructuration process along the extruder for polymeric nanocomposites using the different in-line methods.