Explore the second lecture in a series on Quantum Chromodynamics (QCD) and the physics of the Electron-Ion Collider (EIC) delivered by Marco Radici and Abhay Deshpande. Delve into advanced topics related to proton and neutron structure, quark and gluon distributions, and the fundamental questions the EIC aims to address. Learn about the EIC's potential to investigate nucleon mass composition, spin structure, and gluon saturation in heavy ion collisions. Gain insights into the unprecedented level of detail the EIC will provide in probing hadron structure through its high luminosity and wide kinematical coverage. Suitable for PhD students, postdocs, and junior faculty members in particle physics, QCD, hadron physics, and heavy ion physics.