Presented by Roland Hesse: We present the theory of intense laser-driven ion acceleration from solid targets. Modern experiments using petawatt lasers with pico-second pulses focused to 10^21 W/cm^2 on multi-micron-thick metal targets produce quality energetic jets with billions of 70 MeV protons. We survey the results of contemporary experiments and simulations, identify the key parameters involved in the fundamental physics, detail an end-to-end theoretical framework which explains the ion acceleration process, and discuss key future developments needed for the subject’s advancement.