Quantitative Phase Imaging (QPI) is a label-free approach which not only provides an enhanced contrast on transparent objects, but also enables the extraction of important biophysical cell parameters, such as the dry mass. In this workshop, we will explain how a quantitative phase camera (a.k.a. High-Definition Wavefront Sensor) can be simply implemented by placing a thin diffuser (for instance a piece of scotch-tape) in front of any standard cameras. The diffuser generates a speckle pattern (random distribution of light) on the camera. A fascinating property of thin diffusers, the “memory effect” allows, through a fine tracking of the speckle grains, to precisely quantify the phase distortion at rates compatible with real-time imaging (40Hz). As the method only requires cost-effective, off-the-shelf components, it has the potential to further ease the dissemination of QPI. We will illustrate the implementation of this QPI technique on a commercial microscope and will use it for cells imaging and characterization. We will inspect the acquired QPI images and illustrate their relevance for cells monitoring (and classification).