The GTC (Gran Telescopio Canarias) is an optical and IR telescope, with a 10,4 meter segmented primary, installed at the Observatorio del Roque de Los Muchachos (ORM) on the island of La Palma. GTC commissioning started in July 2007 when First Light was achieved. GTC regular scientific operations started at the beginning of 2009 with its first science instrument: OSIRIS, a visible camera with tunable filter and low-resolution multi-object spectroscopic capability. Since that time science operation and telescope and instrument development activities alternate in using the available telescope time. Later in 2010 the second science instrument will be commissioned: CanariCam, a thermal-IR camera and low-resolution spectrograph with polarimetric and coronagraphic capabilities. This paper presents the telescope commissioning process, the problems encountered and shows some of the performance aspects. First science results will also be presented to demonstrate the current capabilities of the GTC facility.