Enrico Massa is a senior researcher at INRIM specializing in precision measurements and metrology. He has a background in experimental and technological fields and interests in different areas, including optomechanics, low-noise electronics and optoelectronics, mechanical and thermal measurements, measurement and control of atomic-scale displacements, and data acquisition and analysis. Massa's work focused on the lattice parameter measurement for the Avogadro project, which involved using optical and X-ray interferometry, one of the most advanced tools for atomic-scale metrology. Since 1998, Massa has developed groundbreaking technologies for manufacturing split-crystal X-ray interferometers and realigning their lattices. He has also developed atom-scale measurement and control technologies with picometre and nanoradian accuracy over displacement up to 5 cm. These technologies are the only ones capable of achieving the precision required for determining the Avogadro constant and realizing the kilogram by counting the atoms in a perfect silicon sphere. Massa's work was instrumental in the 2019 redefinition of the International System of Units based on fundamental constants. He coordinates INRIM's participation in the International Avogadro Coordination and serves as an Italian delegate at Working Groups and Consultative Committees of the CIPM (International Committee for Weights and Measures).