You can easily switch between the 2 phases using the ‘phase’ toggle button. The breast pump will automatically start in the ‘let-down’ phase when you switch it on and move onto the ‘expression’ phase after 2 minutes. If you wish to go back to the ‘let-down’ phase at any point during the pumping session or if you wish to move onto the ‘expression’ phase before the 2 minutes are up, you just need to push the ‘phase’ toggle button.