The cosmic microwave background (CMB) research told us a remarkable story: the structure we see in our Universe such as galaxies, stars, planets, and eventually ourselves originated from tiny quantum fluctuations generated during the period of “cosmic inflation” in the early Universe, the leading paradigm on the origin of our Universe at ultra high energies. With the WMAP mission we have confirmed many of the key predictions of inflation. Yet, the extraordinary claim requires extraordinary evidence. We seek definitive evidence for inflation by finding primordial gravitational waves from inflation, whose wavelength can be as big as billions of light years. To this end we have proposed to JAXA a new satellite mission called "LiteBIRD", whose primary scientific goal is to find signatures of gravitational waves in the polarisation of the CMB. In this presentation we describe the current state of affairs regarding our understanding of the early Universe, physics of polarisation of CMB, and the LiteBIRD proposal.