Active learning can be used to select a molecule for a chemist to label, from the pool of unlabeled molecules 𝒰. In typical active learning settings, 𝒰 is available before training. In our work, 𝒰 either consists of molecules from a previous molecule generation, or molecules from public databases. The goal in active learning is to learn an accurate model that maps from molecules 𝑥 to labels 𝑦.