Frequency standards characterization facility compared to high-accuracy and high-stability cold atoms optical/microwave clocks.- Scientific support with experimental evidence using the facility (Sr&Yb clock). Facility equipped with optical and microwave signals form the optical and microwave atomic clocks at INRIM. Measurement uncertainty up to < 2E-17 (optical and microwave) Stability:t 2e-15 at 1 second, down to 2e-17 at 1e4 seconds. Equipment colocation in Clean Room (ISO7, and ISO6 upon request)