These uncontrolled fluctuations provide a set of natural experiments to identify cases where humidity affected crystal formation. Figure depicts an illustrative example of the relationship between laboratory humidity and ethylammonium lead iodide, (CH3CH2NH3)PbI3 23 crystal formation. The weak correlation (adjusted R 2 = 0.048) could be attributed to water playing a minor role in crystallization for this system or to other variations between the different experiment batches, such as differences in sampling regimes. Although the dataset contains a complete transcript of all experiments (including typically unreported "failed" reactions ) and experiments were predominantly determined by random sampling (to limit anthropogenic selection bias ), different sampling algorithms were used in this initial dataset. An initial algorithm sampled dispense volumes and was subsequently replaced with an algorithm that performed uniform sampling in the achievable concentration space. The dataset also contains deliberate reproducibility experiments, experimental designs constructed by humans, and experiments guided by machine learning algorithms operating in both exploration and exploitation modes. These different experiment sampling choices may be correlated with seasonal variations in laboratory humidity, and in turn hinder automated serendipity.