Abstract: Various aspects of the early and primordial universe have been probed by the cosmic microwave background (CMB). Large-scale structure (LSS) observations and their theoretical description have now become precise enough to complement these constraints beyond the baryon acoustic oscillation scale. In this talk, I will discuss how careful theoretical consideration of the underlying physics allows us to gain new insights into the early universe from CMB and LSS power spectra. To illustrate this, I will present theoretical background, data analyses and forecasts for the free-streaming nature of neutrinos, primordial non-Gaussianity beyond the local type and oscillatory features in the primordial power spectrum.