The majority of SFB participants have worked in the Jak-Stat field for many years. This allows them to contribute a large number of molecular tools to a common pool. These tools include a huge collection of recombinant Jak or Stat DNAs in expression plasmids or retroviral vectors. GFP-Stat genes in eukaryotic expression vectors and plasmids with other Stat fusion genes for purification purposes are available. Importantly, large numbers of mutants have been generated affecting Jak or Stat phosphorylation, nuclear translocation or interaction with partner molecules. Further available are biochemical tools like purified Stat substrates or anti-Stat/anti-phosphoStat peptide sera.