Transition to turbulence initiated by linear transient growth mechanism in plane Poiseuille flow is demonstrated in the present study. A novel analytical approximation of the linear transient growth mechanism enables us to perform a secondary linear stability analysis of the modified base-flow. Two possible routes to transition will be presented. The first one is initiated by four decaying odd normal modes which form a counter-rotating vortex pair, whereas the second is initiated by five even decaying modes which form a pair of counter-rotating pairs. Because of the minimal number of modes participating in the transition process it is possible to follow the transition stages analytically employing multiple time scale analysis. The analytical results are compared with the direct numerical simulations demonstrating a very good agreement.