Most strikingly, we calculated the accessible chemical space as the number of all possible combinations of discrete parameters used for each category (e.g. reactants, catalysts, etc.). The proportion of accessible space explored is an intensive metric that measures the ratio between the number of chemical reactions experimentally performed and the size of the accessible chemical space. Despite having roughly a similar number of reactions in the three datasets, the accessible chemical space of NiCOlit covers almost a trillion reactions versus less than 20k for both HTE datasets (Fig. ). This indicates that predicting yields on NiCOlit is more challenging than on HTE data. On the other hand, as most of the accessible space has been explored in HTE data (99% and 36% against only 2x10 -7 % for NiCOlit), developing an accurate model for NiCOlit allows to predict yields for a much larger set of unperformed reactions (almost a trillion reactions for NiCOlit).