A telescope is an optical system which collects a lot of light and allows us to “see” objects as if they were much nearer. An astronomical instrument is a very precise tool which analyzes the light, and without this the telescope cannot carry out high level science. For this reason OSIRIS, CanariCam, EMIR, FRIDA and MIRADAS were guests of honor at the “Science with the GTC” conference celebrated in Puebla (Mexico). These are the instruments which are operative, or will be operative on the Gran Telescopio Canarias (GTC)