The United Nations (UN) has declared 2010-2020 the Decade of Biodiversity and, in the Convention on Biological Diversity negotiated in Nagoya, Japan, adopted a strategic plan on global biodiversity. The European Union (EU) has the stated objective to slow the loss of biodiversity and ecosystem services by 2020, and restore as possible the environment in order for the EU to contribute to the maintenance of global biodiversity. The preservation of biodiversity is often associated with the prevention of species extinctions. However, important changes may happen in a species before it goes extinct, for example as a consequence of there being few individuals. These changes may affect how the species interacts with the ecosystem, and may change its ability to reproduce and survive. The importance of genetic diversity for their long term survival is now recognized as crucial, and now one of the official EU criteria for the maintenance of biodiversity is the maintenance of genetic diversity. Although genetic diversity has been recognized by the IUCN as an important component of biodiversity for many years, it has not previously been a part of official EU conservation targets. As this is a new criteria, it is not entirely clear what this means at a practical level. Gen-e provides tools, reference data and examples to help fill this gap.