The most ambitious experiments in fundamental physics push measurement science to its ultimate limits. Detecting a gravitational-wave strain of order 10⁻²¹, or reconstructing the trajectory of a charged particle with micrometer precision inside a multi-storey detector, demands sensors, calibration strategies, and uncertainty budgets that have no parallel in conventional metrology.

This Special Session brings the metrological culture of the IMEKO community into direct dialogue with the frontier instrumentation of gravitational-wave observatories (Virgo, LIGO, KAGRA, Einstein Telescope, LISA) and particle-physics experiments at accelerators (LHC and future colliders). Contributions are welcome that highlight how measurement principles – traceability, uncertainty quantification, calibration, sensor design, and signal processing – underpin the scientific reach of these experiments, and how solutions developed in fundamental-physics laboratories can advance the broader field of measurement science.