On this day in 1917, Asima Chatterjee was born in Calcutta. She became an organic chemist of the patient sort: decades spent asking what the medicinal plants of the Indian subcontinent actually contain, compound by compound, and publishing a great deal of it. She was the first woman to be awarded a Doctorate of Science by an Indian university, and she died in 2006.

One mechanism, kitchen-table version. When a cell divides, it builds a temporary set of ropes inside itself and uses them to haul the two copies of its chromosomes to opposite ends. Those ropes are not solid; they are assembled bead by bead and taken apart again, like a rope you keep splicing and unsplicing as you pull. The vinca alkaloids, from the periwinkle in the photograph below, stick to the beads so the rope cannot be built. The cell that was halfway through dividing simply stops.

Chatterjee worked on the chemistry of those alkaloids, and on antiepileptic and antimalarial compounds besides. What I admire is the method underneath it: no shortcut from a leaf to a medicine, only the long unglamorous business of separating, identifying and checking. Anyone who has spent an afternoon losing a compound on a column knows how many quiet failures sit behind a single clean structure.