The goal of this project is to develop novel types of multifunctional nanoparticles combining temperature diagnostics and therapy. More specifically we aim at combining thermometry in the physiological range with either drug delivery or photodynamic therapy (PDT) all in a single hybrid nanoparticle constructed from Periodic Mesoporous Organosilica (PMO) with lanthanide inorganic nanoparticles grown inside the pores and/or voids of (hollow) PMO particles. For diagnostic purposes temperature measurements in biomedicine are of key importance, as temperature plays an essential role in biological systems. For biomedical applications measurements in the temperature range 20-50 oC are essential (the so- called physiological range). Although detecting the temperature can be done employing robust, and already commercially available techniques, such as thermocouples or infrared imaging, optical temperature measurements at the nanoscale allow to reveal and study phenomena otherwise inaccessible to traditional thermometers such as measuring temperature of cells and even the organelles within them. Theranostics is a recently emerging field of interest, which combines diagnostics with therapy. In this regard, the use of nanomaterials, which allow combining multiple functions in just a single particle, would be able to change the entire healthcare scene and the way certain diseases are treated. However, with the reported up to date nanothermometer materials there is very little room to expand towards multifunctional thermometric materials. We propose a rational design where hollow, porous, biocompatible, multifunctional materials would combine temperature sensing and drug delivery or PDT in a single particle, where the temperature measurements as well as drug delivery/PDT are all controlled through separate wavelength light excitation when the nanoparticles reach the desired location (e.g. cancer cells).