We review a variety of topics related to hadronic structure functions in exclusive
semihadronic tau decays. We introduce the concept of structure functions and
summarize the most important concepts. We then calculate the decay $\tau \to 3 \pi
\nu_\tau$ for very small hadronic invariant mass to one loop in Chiral Perturbation
Theory. New interesting features emerge with respect to the known results at tree
level, in particular for the structure functions $w_D$ and $w_E$. We discuss the
prospects for experimental verification of our predictions. Finally, we discuss
various issues at higher $Q^2$, related to hadronic resonance physics. Here we
consider $2\pi$, $\pi K$, $3 \pi$, $K \pi K$ and $\pi K \pi$ hadronic final states.
