“…CER is still engaging in many activities typical of an emerging field, including curating a core literature [33], publishing first text books [14,41], debating methodology [21,30,50], defining domainspecific methodologies [21,25,41], building domain-specific theories [25,47], discussing publication standards 1 [14,29,50], characterising its research landscape [10,12,32,47], creating its own educational programmes [23], creating a global community [20] and defining career paths for CER graduate students 2 [27,55]. These advances are important, but still leave us wondering "what is CER"?…”