Hybrid composites consisting in a hydrogel matrix with silica micro- and nano-particle reinforcement were produced and characterized. The strategy proposed here to obtain them consisted in a two-step synthesis being the polymer network formation the first step. Porous poly(hydroxyethyl acrylate) hydrogel network was produced by radical polymerization of the monomer diluted in different amounts of ethanol. Polymeric microstructure drives the absorption of a silica precursor solution and the further distribution of the inorganic phase that is formed in situ. A fraction of the resulting silica phase occupies the pores and the other part is in the form of nanoparticles dispersed in the polymer phase. Composites with silica content up to ~ 60% by weight were obtained. Silica phase is continuous and samples maintain their integrity after eliminating the organic phase by pyrolysis. Dependence of hybrid microstructure in compliance, water sorption capacity, bioactivity and the effect of silica content in polymer segmental mobility were assessed. ; COOPEN ; Spanish Ministry of Education [MAT2010-21611-C03-01] ; FEDER ; Generalitat Valenciana [ACOMP/2012/075] ; Instituto de Salud Carlos III (ISCIII) through the CIBER Initiative of the Networking Research Center on Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN) ; Plazas Bonilla, CE.; Gómez-Tejedor, JA.; Perilla, JE.; Gómez Ribelles, JL. (2013). Silica phase formed by sol-gel reaction in the nano- and micro-pores of a polymer hydrogel. Journal of Non-Crystalline Solids. 379:12-20. doi:10.1016/j.jnoncrysol.2013.07.018. ; Senia ; 12 ; 20 ; 379