The present invention relates to magnetic and fluorescent nanoassemblies having reverse architectures. Especially, the nanoassemblies of the invention comprise a fluorescent core and magnetic nanoparticles contacting the surface of the fluorescent core. The nanoassemblies of the invention may further be coated by a polymer, which may optionally be functionalized. The invention further relates to a process for manufacturing the nanoassemblies of the invention. The invention is also directed to the use of the nanoassemblies of the invention, especially for multimodal imaging, in vitro and/or in vivo diagnostics through multimodal imaging, and/or therapy.