Restrictive allograft syndrome (RAS) is one of the most important long-term complications that can occur after lung transplantation. We will use the innovative technology "Single Cell RNA Sequencing" to understand the molecular pathogenesis of RAS. "Single Cell RNA Sequencing" enables the analysis of mRNAs in hundreds of thousands of individual cells. This technology offers previously impossible insights into (diseased) cells, which will then be used to identify aberrant cell populations and their pathological gene expression profiles in the RAS lung. The RAS cell atlas will provide a valuable scientific resource that can be used to develop new molecular RAS therapeutic targets.