Quantum Chromodynamics (QCD) is a non-abelian gauge theory to describe strong forces and is embodied in the Standard Model. The particle-mass generation has a crucial impact over the formation of matter in the Universe after the Big Bang. Spontaneous chiral symmetry breaking generates a large part of the nucleon mass. Simultaneously, the elementary particles of QCD, quarks and gluons, are confined inside their composite states, hadrons. Those non-perturbative phenomena are traced back to the strong QCD interaction in low energy. The current and future experiments using high-energy proton-proton and nucleus-nucleus collisions create a process backward in time, i.e. toward the early Universe. Heavy-ion collision experiments create a hot/dense QCD matter that exhibits quite different properties from the known ground state at low temperature and density. The interior of compact objects in the Universe, such as neutron stars, is another testing ground of QCD at high density. I will give a brief overview on QCD thermodynamics and present recent developments on selected issues.