Gene-specific transcriptional regulation in higher eukaryotes is mediated by complex cis-acting control elements that specify the location, timing and magnitude of the response. During the past five years, an argument has been made that in several cases specificity in gene transcription is achieved by the assembly of higher-order three-dimensional transcription factor/enhancer DNA complexes, termed enhanceosomes. The inherent co-operativity in enhanceosome assembly and the embedded synergy in transcription ensure that a specific gene would be selected for activation only if all the enhanceosome components are present in the same nucleus. Enhanceosomes activate transcription by recruiting chromatin-modifying activities and basal transcription factors to the nearby promoters.