Recently, the muon collider has been recognised as an important option to be considered for the future of particle physics. It is part of the European Accelerator R&D Roadmap developed in 2021 and approved by the CERN Council. Also, interest is increasing in the Americas and in Asia, demonstrated, for example, by the ongoing Snowmass process. The presentation will give an introduction io the muon collider concept and the identified challenges. It will also describe the R&D progress and plans.