The growth rate of cosmic structures is a powerful quantity to probe gravitational interactions and dark energy.
In the late-time Universe the growth rate becomes non-linear, making it more difficult to probe, but also makes it in principle a source of additional cosmological information than its linear counterpart. In this talk, I will discuss why it becomes interesting to probe the growth rate in regions of different density, as well as recent developments in measuring the growth rate using RSD around voids.