Cancer is becoming a very socially important disease. Only in Italy, one thousand of new tumor cases are diagnosed each day according to International Agency for Research on Cancer (IARC) data. Moreover, thousands of lives, that are cut short by cancer, have to be added to the previous numbers. The focal issue is that traditional medicine is actually not able to provide rapid diagnosis, with concrete and effective therapies. With the advent of nanotechnologies, an emerging branch in nanomedecine developed: theranostics. The promise of this new discipline, that exploits functionalized nanoparticles (NPs) to provide both for rapid diagnosis and/or therapies, seems to be the answer for the problem that is represented by cancer.