At Politecnico di Milano, radiation measurement becomes knowledge, from neutrons to ultrafast beams, from dosimetry to tomography, bridging fundamental research and real-world applications. Nuclear Measurements Laboratories (NMLs) focus on studying, applying, and developing methods to exploit or measure radiation fields of different types and properties. Based at Politecnico di Milano, NMLs transform neutrons, photons, and charged particles from ‘invisible agents’ into measurable, traceable information, supporting research, radiation protection, and nuclear applications. Most activities are funded through national and international projects and span spectrometry, dosimetry and microdosimetry of complex and mixed radiation fields, nuclear signal analysis, and the development of innovative detection systems and data workflows. Active neutron spectrometry in complex fields Neutrons represent a particularly demanding frontier, especially under extreme conditions such as those found in fusion facilities, high-energy radiation fields, or pulsed beam environments. The NMLs address these challenges by developing novel active neutron spectrometers, both isotropic and direction-sensitive, through an iterative cycle of advanced simulation (e.g., FLUKA-based modelling) and rigorous experimental validation. One illustrative example is DIAMON: a compact, direction-aware, isotropic, and active …