  In this article, we give a full description of the Wadge degrees of Borel
functions from $\omega^\omega$ to a better quasi ordering $\mathcal{Q}$. More
precisely, for any countable ordinal $\xi$, we show that the Wadge degrees of
$\mathbf{\Delta}^0_{1+\xi}$-measurable functions $\omega^\omega\to\mathcal{Q}$
can be represented by countable joins of the $\xi$-th transfinite nests of
$\mathcal{Q}$-labeled well-founded trees.
