Material science is playing an increasing role in bioengineering and biomedical sciences, aiming to develop new systems and materials capable of overcoming the highly demanding environment of a living organism. One of those materials, Hydroxyapatite (HAp), is the principal calcium phosphate present in the mineral phase of bone. Hydroxyapatite-based materials have been used for dental and biomedical applications, and the control of morphology and structure at micro and nanoscale levels in the synthesis processes, is crucial for several of those applications. Hydroxyapatite crystalline particles were obtained by the so-called sol-gel technique, in which silica gels induce the formation of apatite particles in a simulated body fluid at nearly 37°C, different chemical additives were used to control morphology and particle size, as previously reported by our group. Recently, the synthesis of HAp particles with similar morphologies obtained by different methods, have been reported by other groups. Differences and similarities in morphologies, as well as in the synthesis processes, are established in the present work, along with a discussion of possible crystal growth and assembly mechanisms, which lead to a better understanding of the particle growth processes, is included. This knowledge could be the basis for further synthesis methods aimed to obtain HAp nanostructures with a crystal preferential orientation.