This review discusses the talks presented at the third EMBL Biennial Sym-posium, From functional genomics to systems biology, held in Heidelberg, Germany, 14–17 October 2006. Current issues and trends in various sub-fields of functional genomics and systems biology are considered, including analysis of regulatory elements, signalling networks, transcription networks, protein–protein interaction networks, genetic interaction networks, medical applications of DNA microarrays, and metagenomics.