Abstract: Recent progress in design and fabrication of quantum cascade lasers have brought these devices to operating temperatures in the Terahertz very close to room temperature and very comfortably in the range of Peltier coolers, with the published maximum operating temperature up to 250K. We show also that besides the progress in laser sources, a new concept, the Regenerative Teraherz Quantum Detector enables a simulateous combination of speed and sensitivity for applications.