Where does plastic waste originate? How does it arrive in the Ocean? Where should we concentrate our efforts to stop the flow of this waste? What impacts do plastics have on marine biodiversity? Recent estimates find that 80% of plastic waste found at sea originates on land. The Tara Ocean Foundation and the European Molecular Biology Laboratory (EMBL) have been involved in this research since 2010. Now it is urgent to explore and identify the flux of plastic waste from land to sea in order to stop it. The upcoming Mission Microplastics 2019 — with the CNRS in charge of scientific coordination —will take the schooner Tara through several regions in Europe for 6 months, exploring 10 major European rivers. The journey will begin on May 27, 2019 in Lorient (Morbihan), Tara’s home port.