The chemical precipitation reaction of Ca2+ and phosphate aqueous solution was used to prepare super small hydroxyapatite (HA) nanoparticles in the presence of glucose. A hypothetical "molecular cage" was built in glucose alkaline solution to limit the chemical reaction in a tiny space to control the size and morphology of HA nanoparticles. A possible reaction mechanism of HA nanoparticles confined space synthesis was proposed in this work. Compared with the previous research of the preparation of HA nanoparticles, our work in the first time successfully obtained the surper-small HA nanoparticles which had a 7 nm average size with homogeneous globular morphology. The mild and green synthetic method achieve the low-cost and controllable preparation of super-small nanoscale HA particles. In addition, Zn(OH)(2), Ni(OH)(2), Ag and SiO2 nanoparticles (<10 nm) were also successfully synthesized by this method, indicating "molecular cage" can be appropriate for various nanoparticle synthesis and could become a universally method for the synthesis of nanoparticles. (C) 2017 Elsevier B.V. All rights reserved.