Fluorescence single-molecule (SM) detection techniques have the potential to provide insights into the complex functions, structures and interactions of individual, specifically labelled biomolecules. However, current SM techniques work properly only when the biomolecule is observed in controlled environments, e.g., immobilized on a glass surface. Observation of biomolecular processes in living (multi)cellular environments – which is fundamental for sound biological conclusion – always comes with a price, such as invasiveness, limitations in the accessible information and constraints in the spatial and temporal scales. The overall objective of the BrightEyes project is to break the above limitations by creating a novel SM approach compatible with the state-of-the-art biomolecule-labelling protocols, able to track a biomolecule deep inside (multi)cellular environments – with temporal resolution in the microsecond scale, and with hundreds of micrometres tracking range – and simultaneously observe its structural changes, its nano- and micro-environments. Specifically, by exploring a novel single-photon detectors array, the BrightEyes project will implement an optical system, able to continuously (i) track in real-time the biomolecule of interest from which to decode its dynamics and interactions; (ii) measure the nano-environment fluorescence spectroscopy properties, such as lifetime, photon-pair correlation and intensity, from which to extract the biochemical properties of the nano-environment, the structural properties of the biomolecule – via SM-FRET and anti-bunching – and the interactions of the biomolecule with other biomolecular species – via STED-FCS; (iii) visualize the sub-cellular structures within the micro-environment with sub-diffraction spatial resolution – via STED and image scanning microscopy. This unique paradigm will enable unprecedented studies of biomolecular behaviours, interactions and self-organization at near-physiological conditions.