Resource theorists have racked up scores of theorems over the past decade. But can these abstract theories inform science beyond quantum information and quantum thermodynamics? Can resource theories answer other scientists’ questions about specific systems in the real physical world? We argue affirmatively, illustrating with photoisomers, or molecular switches. Photoisomers surface across nature and technologies, from our eyes to solar-fuel cells. How effectively can these switches switch? This question defies standard tools, because photoisomers are small, quantum and far from equilibrium. We answer by modeling a photoisomer within a thermodynamic resource theory. Using thermomajorization, we upper-bound the switching probability. Then, we compare the bound with detailed balance and Lindbladian evolution. Thermomajorization constrains the yield tightly if a laser barely excites the molecule, such that thermal fluctuations drive switching. We also quantify the coherence in the molecule’s postswitching electronic state. Electronic coherence cannot boost the yield in the absence of extra resources, we argue, because modes of coherence transform independently via thermal operations. This work illustrates how thermodynamic resource theories can illuminate nature, experiments, and synthetics. This work appears in "Fundamental limitations on photoisomerization from thermodynamic resource theories" and was undertaken with David Limmer.