The L4Re Microkernel alias Fiasco.OC is a 3rd-generation µ-kernel (microkernel).

The L4Re Microkernel can be used to construct flexible systems. The microkernel is the base for the L4Re system which supports running real-time, time-sharing and virtualization applications concurrently on one system. The L4Re Microkernel is both suitable for big and complex systems as well as small, embedded applications. We have developed the L4Re Runtime Environment which provides the necessary infrastructure on top of the microkernel for conveniently developing applications. Please refer to the Features page for more information on the capabilities of the microkernel and L4Re overall.