A mechanism and technological process for synthesizing nano-sized crystalline hydroxyapatite. In particular, for producing nano-sized crystalline hydroxyapatite whose particles have nano dimensions in length "l", width "d" and thickness "h", wherein "h" is practically corresponding to the size of one transmission of crystallographic cell a method is disclosed involving the steps of mixing and homogenizing a suspension comprising calcium hydroxide with an amount of phosphoric acid within a first reactor thereby adjusting a defined alkaline pH-value of the resulting mixture, feeding the mixture into a second reactor for causing phase transformations of the mixture and feeding the mixture into a third reactor for providing a suspension by adding a suspension of calcium hydroxide to the mixture to then feed the suspension into the first reactor, whereby each of these steps is cyclically carried out in continuous periodical conditions within at least three stages thereby producing nano-sized crystalline particles of pure hydroxyapatite as a solid phase.