In childhood, adolescence and young adults (CAYA), melanoma is under-studied and non-existing tailored clinical guidelines and standardized approaches lead to a very low diagnostic accuracy. The MELCAYA project aims to understand risk factors and determinants of melanoma to improve the prevention, diagnosis and prognosis of melanomas in CAYAs through a strong international consortium with experts from 10 countries in different disciplines (e.g. oncology, paediatrics, ethics, policy making), and sectors (e.g. academic centers, SMEs, hospitals, patient associations). MELCAYA will work on different approaches. 1) By integrating existing reference European cohorts and registries, studies of genetic and environmental risk factors and progression of melanoma in CAYA will be performed through different omic methods, and a novel taxonomy of CAYA melanoma will be generated. 2) MELCAYA will also develop image-based robust and trustworthy machine learning tools and a pan-European second-opinion platform for better diagnosis specifically designed for CAYA. 3) Moreover, the validation of minimally and non-invasive disruptive tools based on artificial intelligence and volatilomics detection from exhaled breath and skin will lead to earlier detection and more accurate prognosis of melanoma in CAYA. 4) Finally, through the evidence gathered, MELCAYA will design and implement public health strategies and will actively involve patients and the general population. The results of MELCAYA will maximize its impact by making its data and results accessible and re-usable through integration into UNCAN.eu. This action is part of the Cancer Mission cluster of projects on ‘‘Understanding".