Light is now the foundation of many applications that address major societal challenges such as the environment and energy, but also health. The development of diagnostic and theranostic tools for anticancer and antibacterial phototherapeutics is the main objective of the “Fire Light” project. This project is built on a multi-scale approach, from molecular orbital to animal. In particular, the photophysical properties of the compounds will be studied by femtosecond time-resolved spectroscopy and correlated with modelled excited states. The impact and interactions with biological systems will be evaluated in silico, in vitro and in vivo to further enhance this innovative approach to personalised medicine. Beyond the originality of the approach (light-assisted therapy) and the proposed molecular tools (i.e. biphotonic lipids, photothermal nanoparticles, positon and fluorescent fluorinated dual probes), this project aims to create a centre of expertise in photobiology and molecular photochemistry in Lorraine. This centre is based on a truly multi- and transdisciplinary unifying consortium, combining theory with experience and bringing together skills in organic chemistry, physico-chemistry, cellular and molecular biology.