From nucleation to propagation, the earthquake cycle is tightly controlled by fluids in faults. It is today a major challenge to i) upscale laboratory-observed mechanisms to field scales, and i) to constrain field-scale observations using microscopic physics. I will present case studies that allow bridging spatial and temporal scales of the interplay between rocks and fluids across the earthquake cycle. I will show experimental evidence of how contact mechanics can be a powerful tool to upscale the microphysics of dynamic fault slip from micrometer to decimeter scales. Then, I will show how we can use multi-kilometer scale geophysical observations of fluid flow and geomechanical deformation in subsurface reservoirs to constrain laboratory derived earthquake nucleation laws.