biostudies-literatureBounds ADMedical Research Council CanadaMedical Research CouncilEuropean Regional Development Funde202000481https://www.ebi.ac.uk/biostudies/studies/S-EPMC11475348biostudies-literatureUnknown14(5)Multiwell plates (MWPs) are the workhorses of the life sciences. However, biophotonics research with MWPs is limited, in part due to the lack of equipment suitable for photo-irradiation of photoactive molecules in a MWP-suitable, high-throughput manner, either commercially or through open-source MWP systems. Here we present "LightBox", a calibrated controllable MWP illumination system with broad applications including screening of photoactive molecules and characterization of photocatalytic chemicals. LightBox is a high intensity, accurately controllable, uniform illumination system designed for MWPs with electronics and a control unit that provides a simple and intuitive interface. LightBox can reach intensities of 0.23 mW/mm² at wavelengths of 405 nm with variance between wellJournal of biophotonicsLightBox: A multiwell plate illumination system for photoactive molecule characterization.PMC1147534825R16P01361Confidence in Concept awardBounds ADBailey RDAdams CTCallaghan DCGirkin JMfalseLightBox: A multiwell plate illumination system for photoactive molecule characterization.Multiwell plates (MWPs) are the workhorses of the life sciences. However, biophotonics research with MWPs is limited, in part due to the lack of equipment suitable for photo-irradiation of photoactive molecules in a MWP-suitable, high-throughput manner, either commercially or through open-source MWP systems. Here we present "LightBox", a calibrated controllable MWP illumination system with broad applications including screening of photoactive molecules and characterization of photocatalytic chemicals. LightBox is a high intensity, accurately controllable, uniform illumination system designed for MWPs with electronics and a control unit that provides a simple and intuitive interface. LightBox can reach intensities of 0.23 mW/mm² at wavelengths of 405 nm with variance between well2021-01-01T00:00:00Z2021 May2025-04-26T07:57:14.495Z2025-04-06T12:31:46.891ZS-EPMC114753483357656910.1002/jbio.202000481