We present a general hydrothermal method without any organic solvent or surfactant for the synthesis of YBO3:Eu3+ nano- and micro-structures. The samples were of excellent quality with uniform, well dispersed, self-assembled and self-purified YBO3:Eu3+. Single crystal nanoflakes gathered together to evolve into a hierarchical architecture with eight different types of three dimensional morphologies. Strong photoluminescence spectra were obtained at 592, 611 and 627 nm at excitations wavelengths 254 and 363 nm. The emission spectra are associated with the transitions from the excited 5D0 level to the 7FJ (J = 1, 2, 3, 4) levels of Eu3+ activators. YBO3:Eu3+ prepared using ethanol solvent exhibited the highest chromaticity values yet reported.