Surprisingly, the functions of a huge number of microbial genes are still unknown. This knowledge gap can be thought of as ”genomic dark matter” in microbes, and neither computational biology nor current lab techniques have been able address this gap. This challenge has now been tackled through an international collaboration between the Institute for Research in Biomedicine (IRB Barcelona) and two other interdisciplinary research centres, namely the IJS in Ljubljana (Slovenia) and RBI in Zagreb (Croatia).