Refeyn, the pioneer of mass photometry, is delivering a disruptive new generation of analytical instruments that let you weigh individual molecules with light. Mass photometry offers new possibilities to characterise the function, structural composition and dynamics of biomolecules. Refeyn instruments measure the mass of individual molecules directly in solution, rapidly, and simply, revealing the true behaviour of molecules in near-native environments, providing scientists with key information about their mass distribution. Refeyn was spun out of Oxford University in 2018 to make mass photometry available globally. Its technology has now been rapidly adopted across academia and industry, where it is transforming biomolecular characterisation.