The Global Lake Ecological Observatory Network (GLEON) is a grassroots organisation in which limnologists, ecologists, IT experts and engineers have joined forces to establish an international network of lake observatories. The aim of the network is to collect biological, chemical and physical data from all over the world, which is then fed into an online database in near-real time. A public web portal ensures that researchers and the public have easy access to the data obtained. The network helps us to better understand key processes such as the effects of climate and land use change on lakes as well as matter cycles in lakes. The database, which contains many lakes, enables factors that govern the daily, seasonal or annual variable processes of lakes to be investigated at the regional, continental and global level. Lakes Müggelsee and Stechlin were added to the database in 2008.