This will be an observational study to explore differences in pathophysiology between groups of people with and without heart failure (HF) (reduced and preserved ejection fraction) and with and without diabetes mellitus (DM) with a particular focus on cross-talk (fat, muscle, vascular tissue and the heart). The investigators will invite 600 people to partcipate (100 with HFrEF+DM, 100 with HFpEF+DM, 100 with HFpEF-DM, 100 with HFrEF-DM, 100 with DM, 100 without either HR or DM). Special heart scans, exercise testing, blood testing, testing of the automatic nervous system will be performed and in some, samples of fat and muscle and endothelial cells will be collected. These data will be used to create a cohort of well phenotyped patients with a variety of comprehensively collected clinical information, a cell atlas, and a comprehensive assessment of metabolomics, proeomics and cross-talk in between tissues, allowing comparisons between each group.