Symbiotic nitrogen fixation between legumes and rhizobia is the most important nitrogen source for sustainable agriculture. As the final accommodation for rhizobia, the specialized lateral organ, root nodule, that provides the essential microenvironments for rhizobia and its proper development, is vital for biological nitrogen fixation. Nodule de novo organogenesis mainly initiates from cortical cell division and it is generally accepted that cortical cells of legumes possess certain identity, which enables them to respond to and establish symbiosis with rhizobia, but the underlying mechanisms remain unknown. Recently a team led by Ertao Wang in Centre for Excellence in Molecular Plant Science, Chinese Academy of Science showed that the SHORTROOT-SCARECROW (SHR-SCR) module predetermines this cortical cell identity in legumes. This study uncovers a novel molecular mechanism for nodule organogenesis, and provides important clues for an evolutionary understanding of root nodule symbiosis, which is both practically and theoretically valuable for improving nitrogen fixation efficiency in legumes and engineering nitrogen symbiosis in non-legumes.