  We show that thin sheets under boundary confinement spontaneously generate a
universal self-similar hierarchy of wrinkles. From simple geometry arguments
and energy scalings, we develop a formalism based on wrinklons, the transition
zone in the merging of two wrinkles, as building-blocks of the global pattern.
Contrary to the case of crumple paper where elastic energy is focused, this
transition is described as smooth in agreement with a recent numerical work.
This formalism is validated from hundreds of nm for graphene sheets to meters
for ordinary curtains, which shows the universality of our description. We
finally describe the effect of an external tension to the distribution of the
wrinkles.
