Light does not merely activate molecules - it reshapes biology. From the low-energy photons that drive cytochrome c oxidase activity in tissue repair, to the precisely timed illumination that silences a neural receptor or triggers apoptosis in a tumor cell, the biological consequences of light exposure operate across scales from the organelle to the organism. Understanding and harnessing these consequences is the central challenge of contemporary photobiology.

The Italian Society of Photobiology (SIFB) has long stood at the intersection of these questions, uniting researchers who study light as a biological force - not merely as a spectroscopic tool or energy source. Its 2026 Annual Congress (Brescia, 22–24 June) brings together scientists working on how light-driven processes unfold within living systems, and how that understanding can be translated into clinical and therapeutic benefit.

This Research Topic aims to collect the most significant recent advances in the biology of light–organism interactions, with a focus on the cellular, molecular, and tissue-level responses that light elicits in living systems. Three interconnected themes define its scope:

Photobiomodulation and light-driven cellular signalling — Red and near-infrared light interact with endogenous cellular chromophores - most notably cytochrome c oxidase - to modulate mitochondrial function, reactive oxygen species signalling, and downstream gene expression. This theme covers the molecular mechanisms of photobiomodulation (PBM), its effects on tissue regeneration, wound healing, and neuroprotection, and the cell biology underlying its therapeutic potential. Studies characterising how cells sense and respond to non-ionising light, across models from cell culture to animal and clinical settings, are welcome.

Neural photopharmacology, receptor biology, and optogenetics — A rapidly growing community now uses light not to destroy cells, but to interrogate and control them. Photoswitchable ligands targeting GPCRs, ion channels, and neurotransmitter receptors allow reversible, spatiotemporally precise manipulation of neural circuits and signalling pathways. This theme encompasses the photobiology of receptor-ligand interactions under light control; the use of membrane-targeted photoswitches and optogenetic tools to study neuronal excitability, Ca²⁺ signalling, and synaptic plasticity; and the translational potential of these approaches for neurological and pain disorders. The emphasis is on what light reveals and modulates in biology, with the photochemical tool as the means rather than the end.

Cellular mechanisms of photodynamic therapy and clinical photomedicine — PDT achieves its effects through a cascade of photobiological events: photosensitiser excitation, reactive oxygen species generation, and the induction of specific cell death pathways - apoptosis, autophagy, or immunogenic cell death - that determine therapeutic outcome and immune engagement. This theme prioritises the cell biology and mechanistic photobiology of these responses, including subcellular localisation effects, death pathway selectivity, and immune system engagement. Clinical translation - including phototherapy for skin diseases, photodiagnostics, and image-guided interventions - is equally welcome, with an emphasis on the photobiological rationale underpinning clinical protocols.

We welcome submissions addressing, but not limited to:

• Molecular mechanisms of photobiomodulation: chromophore identification, ROS signalling, and mitochondrial photobiology
• PBM in tissue repair, neuroprotection, and inflammatory modulation
• Photoswitchable ligands for GPCR, ion channel, and neurotransmitter receptor control
• Optogenetics and membrane-targeted photoswitches in neural circuit biology
• Spatiotemporal light control of Ca²⁺ signalling and cellular excitability
• Subcellular targets and cell death pathway biology in PDT
• Immunogenic phototherapy: photodynamic activation of anti-tumor immunity
• Clinical phototherapy for dermatological, oncological, and other conditions
• Photodiagnosis and fluorescence-guided clinical interventions
• Porphyrin and tetrapyrrole photobiology in living systems
• Light-driven responses in aquatic phototrophs and natural photobiological systems

Are you interested in contributing a manuscript to this Research Topic?

Illuminating Life: Photobiomodulation, Photopharmacology, and the Cellular Biology of Phototherapy from the SIFB Annual Congress