In this talk, I will describe cosmological probes such as CMB spectral distortions, CMB anisotropy, 21cm distortions as means to probe electromagnetic and neutrino energy injections in pre- and post-recombination universe. I will show that CMB spectral distortions arising out of energetic particle injections have a rich structure and are different from classical thermal or y distortion signature. I will discuss implications of radio photon injections on 21cm global absorption and power spectrum signal. Lastly, I will briefly discuss some recent work utilising fast radio bursts to probe the expansion history of the universe.