Lakes, rivers, estuaries and oceans are closely connected. Despite this, aquatic research is still divided in marine and freshwater sciences. Now, scientists from 19 leading research institutes and universities and two enterprises from 12 countries across Europe aim to change this and have joined forces in the project “AQUACOSM – Network of Leading European AQUAtic MesoCOSM Facilities Connecting Mountains to Oceans from the Arctic to the Mediterranean”. The network will perform the first systematic large-scale experiments in both freshwater and marine ecosystems.