  Consider the energy critical focusing wave equation on the Euclidian space. A
blow-up type II solution of this equation is a solution which has finite time
of existence but stays bounded in the energy space. The aim of this work is to
exhibit universal properties of such solutions. Let W be the unique radial
positive stationary solution of the equation. Our main result is that in
dimension 3, under an appropriate smallness assumption, any type II blow-up
radial solution is essentially the sum of a rescaled W concentrating at the
origin and a small remainder which is continuous with respect to the time
variable in the energy space. This is coherent with the solutions constructed
by Krieger, Schlag and Tataru. One ingredient of our proof is that the unique
radial solution which is compact up to scaling is equal to W up to symmetries.
