the system of the QGP ALICE is using a set of 18 detectors that give information about the mass, the velocity and the electrical sign of the particles. Barrel tracking An ensemble of cylindrical barrel detectors that surround the nominal interaction point is used to track all the particles that fly out of the hot, dense medium. The Inner Tracking System(ITS) (consisting of three layers of detectors: Silicon Pixel Detector(SPD), Silicon Drift Detector(SDD), Silicon Strip Detector(SSD)), the Time Projection Chamber(TPC) and the Transition Radiation Detector(TRD) measure at many points the passage of each particle carrying an electric charge and give precise information about the particle's trajectory. The ALICE barrel tracking detectors are embedded in a magnetic field of 0.5 Tesla produced by a huge magnetic solenoid bending the trajectories of the particles. From the curvature of the tracks one can derive their momentum. The ITS is so precise that particles which are generated by the decay of other particles with a long(~.1 mm before decay) life time can be identified by seeing that they do not originate from the point where the interaction has taken place (the "vertex" of the event) but rather from a point at a distance of as small as a tenth of a millimeter. This allows us to measure, for example, bottom quarks which decay into a relatively long-lived B-meson through "topological" cuts. Inner Tracking System The short-living heavy particles cover a very small distance before decaying. This system aims at identifying these phenomena of decay by measuring the location where it occurs with a precision of a tenth of millimetre. The Inner Tracking System (ITS) consists of six cylindrical layers of silicon detectors. The layers surround the collision point and measure the properties of the particles emerging from the collisions, pin-pointing their position of passage to a fraction of a millimetre. With the help of the ITS, particles containing heavy quarks (charm and beauty) can be identified by reconstructing the coordinates at which they decay. ITS layers (counting from the interaction point): 2 layers of SPD (Silicon Pixel Detector), 2 layers of SDD (Silicon Drift Detector), 2 layers of SSD (Silicon Strip Detector). The ITS was inserted at the heart of the ALICE experiment in March 2007 following a large phase of R&D. Using the smallest amounts of the lightest material, the ITS has been made as lightweight and delicate as possible. With almost 5