  Ultra-peripheral collisions (UPCs) of ions allow us to study photonuclear and
two-photon interactions at energies above those available at fixed target
accelerators. For heavy ions, the couplings are large enough so that
multi-photon interactions are possible, and higher order corrections are
expected to be significant. In this writeup, I present some recent UPC results
from the Relativistic Heavy Ion Collider (RHIC), and discuss some future
prospects. I also draw parallels between UPC data and that expected at an
electron-ion collider (EIC), and show how UPCs are a useful lead-in to EIC
physics. This writeup is based on a talk at "Initial State 2014," (IS2014),
with a focus on the newest results. One important result is that comparison of
the RHIC (and LHC) results on coherent $\rho^0$ photoproduction show evidence
for nuclear suppression, compared to a calculating based on $\gamma p$
cross-sections.
