PETiPIX is an ultra high spatial resolution small animal PET scanner designed for scanning of mouse brains. It utilises four state of the art pixellated silicon detectors, Timepix, in an edge-on configuration to provide a field of view (FoV) 15 mm in diameter. Each Timepix detector consists of 256×256 pixels, with pixel dimensions of 55μm×55μm× 300μm. Monte Carlo simulations have been carried to evaluate the performance of the proposed scanner. The simulated scanner achieved an overall spatial resolution of 0.29 mm (measuring at full width at half maximum (FWHM)) with a sensitivity of 0.01%. Two separate phantom studies (hot phantom and cold Jaszczk phantom) have been performed and their results demonstrate that PETiPIX is capable of achieving a high spatial resolution across its full FoV. Preliminary experiments recording recoil electrons tracks from Compton scattering events agree with the simulation results. Experiments involving two synchronised Timepix modules with a 68Ga point source placed in the centre of the FoV demonstrated the capability of PETiPIX prototype to record true coincidence events.