One dimensional spin chains systems represent an ideal place to study a wide range of non perturbative phenomena such as exotic phases, fractional excitations and statistics. A method to study these systems is the so called Matrix Product States, which provides an ansatz for the ground state and excitations. The MPS method exploits the entanglement properties of spin chains but it is limited to describe systems with short range entanglement. For this reason it cannot properly describe critical systems where the entanglement entropy grows with the size. In this talk we shall present an extension of the MPS which overcomes this difficulty using Conformal Field Theory. The ansatzs so obtained have strong resemblences with the Laughlin wave function of the Fractional Hall effect.