This article comments on: Arrivault S, Moraes TA, Obata T, Medeiros DB, Fernie AR, Boulouis A, Ludwig M, Lunn JE, Borghi GL, Schlereth A, Guenther M, Stitt M. 2019. Metabolite profiles reveal inter-specific variation in operation of the Calvin–Benson cycle in both C4 and C3 plants. Journal of Experimental Botany 70, 1843–1858.SNS