Platelets are small anucleated blood cells involved in the healing of wounds. Platelet concentrates from blood donations are used by clinicians to treat thrombocytopenia, a condition characterized by  an insufficient platelet blood count and increased risk of bleeding. Short shelf-life, donor shortage, immunogenicity and high collection costs represent the main limits of transfusion therapy and drive the demand for alternative platelet sources. Platelets originate from large bone marrow cells called megakaryocytes (MK), that extend filaments in the blood circulation. The flow-driven elongation and rupture of these filaments yields platelets. We mimick this process in microfluidic chips. MKs are injected into microchannels where adhesive pillars act as biochemical anchors while cells are exposed to flow. We visualise the entire platelet formation process, from the initial capture of a flowing MK upon its encounter with a pillar to the formation of elongations and finally to the release of (pro)platelets in the flowing media. Our goal is to elucidate the interplay between hydrodynamic forces and cytoskeleton remodeling during platelet formation.