摘要This paper presents a comprehensive overview of the historical trajectory and development in biophoton studies over the past 100 years, with a particular focus on the recent progress regarding the pivotal role of biophoton in mediating radiation-induced bystander effects (RIBE). The exploration of biophoton mystery starts from the initial observation of mitogenetic radiation and continues to develop to the contemporary science of biophotonics. The properties and underlying mechanisms of biophoton emission are described with illustrative examples from diverse biological systems such as plants, animals and humans. The conclusive evidence of cell-to-cell communication facilitated by biophoton signaling is presented, followed by an elaborate interpretation of potential mechanisms through which biophoton mediates RIBE. The engagement of mitochondria and exosomes in this process is extensively clarified, by highlighting their significant roles in biophoton-mediated RIBE. The advances in biophoton research in respect of bystander response to ionizing radiation may offer profound insights into radiobiology and provide for possible future applications as well in radiation medicine and protection.