Schematic of the Bayesian physical forward-modeling framework of BORG, which solves a large-scale Bayesian inverse problem by fitting a dynamical structure formation model to galaxy observations and subsequently inferring the primordial initial conditions (ICs) that lead to the formation of the presently observed cosmic structures via gravitational evolution. The BORG forward-modeling approach naturally marginalizes over unknown galaxy bias and accounts for all relevant physical effects, such as redshift space distortions (RSDs) resulting from the peculiar velocities of galaxies, as well as instrumental selection effects.