Structure of viruses • Most viruses are too small to be seen under light microscope. • All viruses consists of an RNA or DNA core genome surrounded by a protein coat capsid. • The combined viral genome and capsid is called the nucleocapsid.Structure of viruses • Most viruses are too small to be seen under light microscope. • All viruses consists of an RNA or DNA core genome surrounded by a protein coat capsid. • The combined viral genome and capsid is called the nucleocapsid