(A) Herpes virus capsids are assembled in the nucleus and then bud through the inner nuclear membrane, acquiring a membrane coat. They then apparently lose this coat when they fuse with the outer nuclear membrane to escape into the cytosol. Subsequently, they bud into the Golgi apparatus, and bud out again on the other side, acquiring two new membrane coats. The virus then buds from the cell with a single membrane when its outer membrane fuses with the plasma membrane. (B) Vaccinia virus, which is closely related to the virus that causes smallpox, is assembled in “replication factories” deep within the cytosol. The first structure assembled contains two membranes acquired from the Golgi apparatus by a poorly defined wrapping mechanism. A variable proportion of these viral particles are then engulfed by the membranes of a second intracellular membrane-enclosed compartment. These viral particles have a total of four layers of membrane envelope. After fusion at the plasma membrane, the virus escapes with three membrane layers.