The Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Lab can provide collisions with various ions (from Deuteron to Uranium) and polarized protons. In its 15 years operations, the luminosity have been increased tremendously due to several upgrades: a new ion source, Bunch merge in the injectors, stochastic cooling in RHIC, e-lens for beam-beam compensation. R & D effort is also ongoing to make an electron ring to collide with existing ion beam as electron ion collider.