Illustration of the life cycle of smallpox. At right smallpox particles are binding to and entering the cell. At far right are immature virus particles (without an envelope), with mature virus particles (with an outer envelope) to their left. Both shed their outer layers, depositing the core nucleoprotein (blue) that contains the DNA (deoxyribonucleic acid) genome of the virus in the infected cell's cytoplasm. The virus then makes many copies of itself. As the virus buds (left) from the host cell it takes part of its membrane as an envelope.