Multi-Spectral and Photon-Counting x-ray imaging is an emerging technique with the potential to change the routine clinical practice and represents a paradigm shift that has already secured its position as the most significant innovative step in the field of medical x-ray imaging and CT. Most recently US Food and Drug Administration (FDA) has called it “the first major imaging device advancement in CT in nearly a decade”. All major healthcare manufacturers have made large investments to commercialise this spectral photon-counting technology, and hence, this very promising imaging technique is on the verge of becoming clinically available. The concept of multispectral photon-counting x-ray imaging is based on a completely novel semiconductor detector, which pushes technology to its limits overcoming the limitations of current CT detectors. Multispectral and photon-counting x-ray imaging technique is a breakthrough in medical imaging transferring x-ray imaging into a real quantitative and, by using novel targeted contrast agents, into a molecular imaging modality offering unprecedented benefits compared with conventional CT and opening up new horizons. During the presentation an overview of the basic technical principles, current status, limitations and challenges and potential clinical applications and benefits of multispectral and photon-counting CT will be given.