Among its many important effects, the hormone insulin binds to antennas on heart and skeletal muscle cells and transmits a signal inside to open doorways called GLUT4 in the cells to allow glucose to enter. The ability of insulin to stimulate glucose entrance fails in a process called insulin-resistance. Insulin resistance contributes to the early development of type 2 diabetes and cardiovascular disease and prevention and treatment strategies are therefore desirable. Insulin resistance is commonly explained by the insulin antenna failing to transmit its signal, but we suspect – based on preliminary work – that the inside of cells becomes progressively messier in insulin resistance and that GLUT4 is instead moved out of reach of the insulin signal. To test this idea in-depth in humans, we will develop new advanced microscopy tools to analyse human skeletal muscle biopsies and human 3D stem cell models of heart and skeletal muscle.