Studying behaviours of cells in their natural living state is very important for biological research. However, these specimen are phase objects and are hardly visible under conventional light microscope. From a series of light microscope images, one can obtain high-contrast and detailed phase images by solving the transport-of-intensity equation (TIE). In this project, we would like to develop an ImageJ plug-in implementing a new phase imaging algorithm that is based on TIE. The utility of the method is going to be validated on real data experiments.