In vivo transfer and expression of foreign genes allows for the elucidation of functions of genes in living organisms and generation of disease models in animals that more closely resemble the etiology of human diseases. Gene therapy holds promise for the cure of a number of diseases at the fundamental level. Synthetic "nonviral" materials are fast gaining popularity as safe and efficient vectors for delivering genes to target organs. Not only can nanoparticles function as efficient gene carriers, they also can simultaneously carry diagnostic probes for direct "real-time" visualization of gene transfer and downstream processes. This review has focused on the central nervous system (CNS) as the target for nonviral gene transfer, with special emphasis on organically modified silica (ORMOSIL) nanoparticles developed in our laboratory. These nanoparticles have shown robust gene transfer efficiency in brain cells in vivo and allowed to investigate mechanisms that control neurogenesis as well as neurodegenerative disorders.