More than 1,000 autonomously bioluminescent organisms have been discovered in nature, many of which are believed to produce light through the luciferin-luciferase reaction. We have been working on developing unnatural luminescence properties of firefly bioluminescence, to effectively apply this natural phenomenon in basic biomedical research. During this process, we successfully developed synthetic firefly bioluminescence reactions that generate near-infrared (NIR) light, which is not found in nature, significantly improving the sensitivity of deep tissue imaging (Nat Commun 2016, 7, 11856, Science 2018, 359, 935). Further technological advancements are anticipated to enable the visualization of biomolecular dynamics through near-infrared bioluminescence reactions. To this end, we are pursuing the development of NIR bioluminescent sensors by incorporating biomolecular sensing functions into synthetic firefly luciferases. In addition, we are seeking to identify synthetic bioluminescence reactions harnessing longer wavelengths and higher brightness to meet emerging needs in biomedical research(Int J Mol Sci 2024, 25, 7338).