Fluid colloidal crystals comprising a solid-liquid dispersion electrostatically charged at not more than 2000 .mu.S/cm in terms of an electrical conductivity, wherein the solid-liquid dispersion comprises, as a dispersoid, electrostatically chargeable spherical colloidal particles of an organic or inorganic polymer having a mean volume diameter (d) of not more than 30 .mu.m, and as a dispersion medium, an aqueous solution or a dissolving water-containing non-aqueous solution, the dispersion concentration of the spherical colloidal particles is not more than 70%, around the dispersoid an electric double layer of a given thickness (.DELTA.e) is formed, and the spherical colloidal particles form a three-dimensionally ordered lattice that shows fluidity and is a particle array structure in which the colloidal particles are aligned longitudinally and laterally in a lattice form while an interparticle distance (L) defined as a distance between centers of the particles arranged opposite to each other along the center line satisfies the relationship (d)<(L).ltoreq.(d)+2(.DELTA.e). A process for producing a three-dimensionally ordered lattice, comprising drying the fluid colloidal crystals to form a three-dimensionally ordered lattice which is a homogeneous particle array structure constituted of the organic or inorganic monodisperse spherical fine particles of the dispersoid.