In this talk I will sketch how we can test gravity with unprecedented precision by combining new gravitational wave measurements, observational bounds from cosmology, and novel particle theory inspired insights, in particular allowing us to zoom in on the nature of dark energy. In doing so, I will highlight the interplay between gravitational wave constraints on gravity post-GW170817, data constraints from cosmic microwave background and galaxy clustering measurements, and novel theoretical priors on such theories (ranging from purely classical stability requirements to radiative stability- and positivity-related priors). [please email a.held@imperial.ac.uk for zoom link or password]