In the 6G SENTINEL project, the five participating Fraunhofer Institutes are developing key technologies for the impending 6G mobile communications standard. To this end, they are working on further improving the data rates, availability, accuracy, service quality and reliability of mobile communications. 6G SENTINEL aims not only to push existing 5G technologies further, but also to develop brand new approaches that will help applications such as virtual reality, digital twins and autonomous driving achieve a genuine breakthrough with 6G. The top priorities are to exploit terahertz frequencies and develop technology for more flexible networks, in particular by incorporating satellites and flying platforms.