Secondary anisotropies of the cosmic microwave background (CMB) are known to be remarkable probes of cosmology. The properties of free streaming CMB photons from the surface of last scattering are altered by their interaction with matter in the Universe carrying crucial information about the origin, growth, and evolution of structures and also the epoch of reionisation. In this talk, I will discuss the potential of these secondary anisotropies, namely the thermal and kinematic Sunyaev-Zeldovich (SZ) effects and the gravitational lensing of the CMB, to shed light into some of the long-standing cosmological quests like the properties of dark energy, neutrino masses, and the physics of reionisation. I will also present the challenges posed by astrophysical foregrounds for the detection of these small-scale anisotropies and discuss strategies for mitigating them. Finally, I will present results from a recent work to constraint models of reionsation with kSZ using the South Pole Telescope and end by showing the prospects of SZ/lensing science with future CMB surveys like the CMB-S4 experiment.
