We developed an original reproducible 3D-technology for preparation of single dormant microspheres consisting of 2000 somatic cells. The dynamics of microsphere assembly from mesenchymal and epithelial cells of retinal pigment epithelium was traced using time-lapse microscopy: formation of a loose aggregate over 24 h followed by its gradual consolidation and formation of a compact viable microsphere with a diameter of 100-150 μ by day 7. The cell number in the formed microspheres remains unchanged. Reactivation observed upon fusion of epithelial and/or mesenchymal microspheres results in the formation of a united compact microtissue. The fusion dynamics reproduces spherogenesis irrespective of the initial amount of co-cultured microspheres. Reactivation via two-step induced angiogenesis opens new prospects for production of vascularized microspheres and microtissues.