Zhang, Y. JACoW Geneva, Switzerland Electron-Ion collider (EIC) utilizes deep-inelastic scatterings to probe structures of nucleus. HERA, the only e-p collider ever built and operated, ended its science program in 2007. Over the past 15 years, 7 next generation EICs were envisioned worldwide for high energy and nuclear physics. In the US, two electron-ion colliders, eRHIC and JLEIC, have been proposed in BNL and JLab respectively. The US EIC designs were guided by the science program (EIC White Paper). The US NSAC Long Range Plan (2015) recommended EIC as the next major facility in US for QCD frontier. If approved by DOE, construction will likely be completed around 2025. Cooling of proton/ion beams is essential for eRHIC and JLEIC to reach luminosity above 10³⁴/cm²/s. It enables emittance reduction up to an order of magnitude in all dimensions. eRHIC adopts the novel Coherent-electron-Cooling (CeC) concept. JLEIC has chosen magnetized electron cooling for the baseline, utilizing a multi-stage cooling scheme. Both CeC and high energy magnetized EC are under active development: BNL plans to conduct a proof-of-principle test of CeC at RHIC next year; JLab focuses on a technical design and technology development for a high energy bunched beam electron cooler based on ERL and circulator ring.