A main challenge that significantly impedes REBa 2Cu 3O x (RE = rare earth) coated conductor applications is the low engineering critical current density J e because of the low superconductor fill factor in a complicated layered structure that is crucial for REBa 2Cu 3O x to carry supercurrent. Recently, we have successfully achieved engineering critical current density beyond 2.0 kA/mm 2 at 4.2 K and 16 T, by growing thick REBa 2Cu 3O x layer, from ∼1.0 μm up to ∼3.2 μm, as well as controlling the pinning microstructure. Such high engineering critical current density, the highest value ever observed so far, establishes the essential role of REBa 2Cu 3O x coated conductors for very high field magnet applications. We attribute such excellent performance to the dense c-axis self-assembled BaZrO 3 nanorods, the elimination of large misoriented grains, and the suppression of big second phase particles in this ~3.2 μm thick REBa 2Cu 3O x film.