The reaggregate approach involves the regeneration of histotypical three-dimensional spheres from dispersed cells of a given tissue in suspension culture. Reaggregated spheres are used as tumour, genetic, toxicological, biohybrid and neurosphere models, and often replace animal experimentation. A particularly instructive example is the use of reaggregation to regenerate complete laminar tissue from avian embryonic retina. By revealing constraints of layered tissue formation, such retinal spheres could be instrumental for regenerative medicine, including stem cell-based tissue engineering.