It is interesting that the natural phenomenon of chelator citrate stabilizing nanocrystals in bone could be learned and utilized in manipulating man-made nano-materials. During the synthesis of upconversion luminescent fluorides, it appeared that, the more citrate participated, the more difficult the resultant material transformed from cubic phase KY F nanocrystals, through hexagonal KYF , to orthorhombic YF crystals or mesocrystals, which clearly indicates the critical role of citrate in stabilizing KY F nanocrystals. Particles with different size, morphology, composition, and phase were controlled through the only variation of citric acid content. Meanwhile, the self-assembled mesocrystals showed emergent luminescent property with 63 times higher intensity, compared with the nanocrystals. The same sized YF single crystals and YF mesocrystals also exhibited dramatic difference in luminescent intensity. © 2013 Elsevier B.V.