The ubiquitous nuclear adaptor protein LIM‐domain‐binding protein 1 (Ldb1) was originally identified as a cofactor for LIM‐homeodomain and LIM‐only (LMO) proteins that have fundamental roles in development. In parallel, Ldb1 has been shown to have essential functions in diverse biological processes in different organisms. The recent targeting of this gene in mice has revealed roles for Ldb1 in neural patterning and development that have been conserved throughout evolution. Furthermore, the elucidation of the three‐dimensional structures of LIM–Ldb1 complexes has provided insight into the molecular basis for the ability of Ldb1 to contact diverse LIM‐domain proteins. It has become evident that Ldb1 is a multi‐adaptor protein that mediates interactions between different classes of transcription factors and their co‐regulators and that the nature of these complexes determines cell fate and differentiation.