This document presents MIDATA.coop, a citizen-controlled platform for storing and sharing personal health data. MIDATA.coop is being developed by ETH Zurich and Bern University of Applied Sciences as a not-for-profit cooperative that empowers citizens to securely store their medical and genomic data and share it through mobile apps if they choose. The presentation outlines several potential use cases for MIDATA.coop, including patient follow-up after medical procedures, post-surveillance of chronic conditions like multiple sclerosis, and health data sharing for athletes, students and researchers.