Model cells viewed under a light microscope. (left are transmitted light images, right are fluorescence). Top panels show spherical structure that has two different types of lipid molecule in the membrane (red and green), as well as two different polymers in the aqueous interior (one of the polymers is labeled blue, the other polymer is unlabeled). Both the lipid membrane and the aqueous interior are phase-separated into coexisting microdomains that have different chemical compositions. In the lower panels, a sucrose solution has been added outside the model cell, such that it loses water due to osmosis, concentrating the polymer solution inside. The structure buds, with the different lipid and aqueous phase domains going to opposite ends, providing a very simple chemical polarity to the model cell. Scale bar is 10 micrometers.