A a great deal of experimental and theoretical progress has been achieved in our understanding
of partonic structure of hadrons in recent decades. I will discuss our current understanding  of
hadron structure from the point of view of Quantum Chromodynamics, the theory that describes
the hadron as dynamical system of partons (quarks and gluons). I will emphasize the emerging
concept of 3D (three-dimensional) parton distributions and discuss their formal definition,
evolution, and phenomenology.  Jefferson Lab 12 will play crucial role in experimental measurements
of hadron structure. I will explain details of the program and show the potential of future
measurements. I will also discuss future of nuclear physics beyond Jefferson Lab 12 at a proposed
Electron-Ion Collider.