'If I'd discovered metformin, I'd have tossed it aside...'

What is chemical intuition? One example would be the ability, won through experience, of a chemist to look over a set of compounds and sort them (however roughly) into the ones that are more or less likely to be of interest for some purpose. I work in drug discovery, so the examples that I see tend to be questions such as: ‘What compounds should be in our screening libraries?’ and: ‘Which of these hits from the assays should we spend more time on?’ But the same process applies to people in materials science, polymers, coatings, energy applications and all parts of chemistry. We’re all faced with more options than we can possibly follow up on, and we need to work on the ones that are more likely to lead to something useful. Over time, we work on successful projects and, inevitably, not so successful ones, and we naturally take note of those compounds and classes that have been useful and the ones that have led us astray.