In our everyday world, quarks and gluons, forever hide inside protons and neutrons.
While their fundamental properties are encoded in the theory of quantum chromodynamics
(QCD), many phenomenological aspects of QCD dynamics remain poorly understood.
When gluons are massless and the quarks carry only a small fraction of the mass of
a nucleon, how do nucleons acquire their large mass? How does nuclear matter emerge
from the hot quark-gluon plasma that permeated the universe shortly after the Big Bang?
What are the limits of ordinary nuclear matter at high density, e.g. in the interior of neutron
stars or neutron star mergers? My talk will explain where our investigation of these questions
stands, aided by experiments at the Relativistic Heavy Ion Collider and elsewhere, and how
future facilities, such as an Electron-Ion Collider can help us finding the answers.