Chemically and/or genetically engineered viruses, viral capsids and viral-like particles carry the promise of important and diverse applications in biomedicine, biotechnology and nanotechnology. Potential uses include new vaccines, vectors for gene therapy and targeted drug delivery, contrast agents for molecular imaging and building blocks for the construction of nanostructured materials and electronic nanodevices. For many of the contemplated applications, the improvement of the physical stability of viral particles may be critical to adequately meet the demanding physicochemical conditions they may encounter during production, storage and/or medical or industrial use. The first part of this review attempts to provide an updated general overview of the fast-moving, interdisciplinary virus engineering field; the second part focuses specifically on the modification of the physical stability of viral particles by protein engineering, an emerging subject that has not been reviewed before.