We present a simple microfluidic device able to trigger the nucleation of the crystals at specific locations on the microchip for the statistical study of protein crystallization. The microsystem is an array of independent PDMS microchambers connected to a fluid-dispensing channel. The chambers are filled with a crystallizing aqueous protein solution and then sealed with a fluorinated oil phase. Each chamber presents a small oil/water interface at the connection with the main channel. The crystals most likely grow near the interface, allowing a microscopic observation of the nucleation events at specific positions on the chip. For the sake of demonstration, the method is applied to the crystallization of HEW lysozyme.