Background: Fluorescent proteins have continued to shed light on cell biology since the cDNA of wild type green fluorescent protein was first isolated. Nowadays, these remarkable proteins are useful tools, not only in basic research, but also in clinical medicine. Highlight: By taking advantage of fluorescent protein-based technologies, we identified a signaling network critical for influenza virus internalization and infection. In addition, we developed a highly sensitive biosensor for monitoring kinase activity that utilizes energy transfer between fluorescent proteins. This has led to a high-performance clinical test that enables the prediction of future therapeutic responses and the risk of acquired drug resistance for each individual patient before beginning molecular target therapy. Conclusion: Technologies that utilize fluorescent proteins, such as the biosensor presented here, should find increasing applications in clinical medicine. (C) 2016 Japanese Association for Oral Biology. Published by Elsevier B.V. All rights reserved.