OPT models of CS12 to CS23. Still shots of the left lateral side of 3 dimensional OPT models of human embryos spanning the major period of organogenesis (CS12-CS23). The developmental stage (e.g. CS12), specimen number (e.g. N285) and karyotype for each model are given underneath. The movies for all of these models can be viewed at http://www.ncl.ac.uk/ihg/EADHB/ . The full models for all stages are available on request.