The exposome chemical space is the chemical subspace to which humans are exposed to from conception to death. The exposome chemical space is mostly unknown and may include human-made and natural chemicals as well as their transformation products. The efforts to explore/map the exposome chemical space have been divided into computational and experimental. The computational approaches focus on building chemical databases of mainly human-made chemicals and then ranking (i.e. chemical prioritization) those structures based on the available metadata (e.g. volume of production). As for the experimental strategies, the focus has been on actively measuring the chemicals in different environmental compartments, including the transformation products. Computational Approaches for Database Building