Proffesor Klein's main scientific activities are in the area of electromagnetic material characterization and sensor applications, but also on microwave and terahertz devices for communciation and sensing. One current focus is on graphene and related 2D materials, where Norbert is currently establishing a cluster system for 4" graphene growth by chemical vapour deposition. The other focus is on microwave-to-terahertz biosensing, in particular blood analysis by microfluidic-resonator assemblies and single cell detecion in biological liquids. Norbert has developed practical sensors for security applications - based on earlier work on microwave filters and oscillators for mobile communication, and he holds more than 15 patents. In 2007, he spun out a company (EMISENS), which successfully commercializes a microwave based bottle scanner for airport checkpoints.