The self-assembly of well-defined polypeptide-based diblock copolymers into micelles and vesicles is presented. The stimuli-responsive behavior of polypeptides to pH and ionic strength is used to produce stimuli-responsive nanoparticles with a control size and shape. Results focusing on vesicles obtained from polypeptide-based diblock copolymers that are particularly promising for biomedical application will be detailed by means of static and dynamic light scattering analysis, UV circular dichroism, NMR and small angle neutron scattering experiments. Also systems that are able to form vesicles with narrow size distributions at basic and acidic pH going through an intermediate state of single polymer chains are presented. These nanoparticles are particularly interesting for encapsulation and delivery purposes at a controlled pH. Finally, surface self-assembly of micelles and vesicles will be shown as models for biological surfaces such as mucosal surfaces.