Quantum Chromodynamics (QCD), the theory of the strong interaction, is a remarkable quantum field theory, giving rise to interesting emergent phenomena. For many of these we are still seeking to unravel their precise nature, including confinement - whereby quarks and gluons are trapped inside relativistic bound states like the proton - and hadronization - whereby energetic quarks and gluons produced in a high energy collision evolve into bound pions and other hadrons. In this talk I discuss new insights into QCD obtained from the study of transverse momentum dependence, including the distributions of confined and hadronizing particles, final state interactions, and spin-momentum correlations. This multi-faceted program relies on foundational results in continuum field theory, lattice QCD calculations, experimental measurements, and phenomenological analyses. The bright future of this field will be particularly influenced by the upcoming electron ion collider at BNL.