KYCC: Pyridine & Jubilant Ingrevia

Picture a benzene ring: the six-carbon hexagon everyone remembers from school chemistry. Now knock out one carbon and put a nitrogen atom in its place. That is pyridine. One small swap, and the molecule behaves completely differently: it becomes mildly basic, it dissolves in water, and most usefully, it becomes a very convenient building block for hanging other things off.