The success of quantum field theory (QFT) rests on a couple of spontaneous symmetry-breaking inspired particle physics models. One recognises the fundamental property named Confinement, meaning its underlying fields (quarks, gluons) never appear as asymptotic states, as the key pillar of Gell-Mann's quantum chrome-dynamics (QCD) theory. QCD describes quarks-mediated-by gluons strong interactions, owning colour charge. It's known as the SU(3) gauge theory (one where the force carriers transform as vectors under the Lorentz group) of the current standard model for elementary particles (quarks/leptons) and forces, SU(3)×SU(2)_{L}×U(1), encompassing the strong, electromagnetic, and weak interactions. (The QCD symmetry group, having eight conserved charges (8l.i.gluons), is referred to as colour SU(3).) The theory offers a self-consistent explanation why quarks/gluons are the fundamental particles that make up composite hadrons (protons/neutrons/pions...), constituents of almost all existing matter in the universe. One also identifies the Weinberg-Salam-Glashow authored electroweak theory, which provides a sound description of the massive vector bosons charged W^{+} and W^{-} and chargeless Z^{0} (and the photon Y) via the electroweak symmetry breaking SU(2)×U(1)_{Y} --- U(1)_{em} affected by the Higgs mechanism. (Here the neutral complex scalar doublet Higgs field, -whose ground state corresponds to an excited nonzero vacuum expectation value (VEV) state-, breaks the electroweak symmetry and subsequently interacts with previously (four) massless particles to give them mass.) Three components (Goldstone bosons) of the Higgs field become part of the massive W/Z bosons. The remaining one becomes the Higgs boson itself. The massless quarks interact with the Higgs field nonzero VEV, and the resulting positive potential energy becomes what is measured as quark rest masses. This model merges electromagnetism and (charged-current, neutral-current; leptonic, semi-leptonic, hadronic) weak interactions into a single scenario above the unification energy-scale 246 GeV (temperature ~10^{15} K), defining the quark epoch in the primeval universe. Mathematically, the weak interactions -featured by its unique flavour-changing are unified with electromagnetism via a Yang-Mills field with SU(2)×U(1) gauge group. Such group defines the formal operations that can be applied to the electroweak gauge fields (weak isospin W_{1}, W_{2}, W_{3} -for interactions with W^{+,-}, and weak hypercharge B -for interactions with Z^{0}) without changing the dynamics of the system. Such invariance is known as electroweak symmetry.) The electroweak interaction was firmly experimentally established via the discovery of neutral currents in neutrino scattering and proton-antiproton collisions. Meanwhile, over the years it has been dwelt on that the general theory of relativity and the quantum theory of fields cannot be "fused" into kind of a quantum theory of gravitation. In special because of the lack of clues from nature about which direction to pursue; and in virtue of the energy scales needed for testing it. Such assertion isn't correct as concerns semi-classical gravity (although it isn’t the sort of theory that the physics community is comfortable with) because it works quite well as properly computing the expectation values for the field's dynamics. A prospective pathway to run on to unify gravitation and QFT as presently sought-after can be, concomitant to the era of precision cosmology, the gravitational-wave (GW) astronomy initiated by LIGO/VIRGO Coll. (2015); being GW cosmological/astrophysical backgrounds feasible goals. With the advent of these research frontiers, forthcoming decades promise edit avenues to better understanding the universe. This triggers us to welcome researchers in these fields to contribute original or review papers to be published in chapters of this special volume on crossroads wherein QFT, astroparticle physics, and GW astronomy may converge to guide us to momentous breakthroughs about how the universe truly works.