# What is the smallest range at which we have measured the effects of gravitational force between two masses?

We know that two independent bodies exert gravitational pull towards each other. We have confirmed that gravitational force acts at planetary level (i.e. between the Moon and the Earth). It has been even confirmed to act a distance of few meters. What the minimum distance that we have gone and confirmed the effect of gravitational pull. Is the gravitational pull still acting between the electron and proton of a Hydrogen atom(however small it may be)?

Is it possible that the gravitational force acts on even smaller scales?