  These notes focus on the Lipschitz geometry of sets that are definable in
o-minimal structures (expanding the real field). We show that every set which
is definable in a polynomially bounded o-minimal structure admits a
stratification which is locally definably bi-Lipschitz trivial along the
strata. This result is obtained as a byproduct of two foregoing results of the
author. The first one asserts that, given a family definable in an o-minimal
structure, there is a regular vector, up to a definable family of bi-Lipschitz
homeomorphisms. The second one is a bi-Lipschitz version of the famous Hardt's
theorem. We give proofs of these two theorems that avoid the use of the real
spectrum. The article recalls the basic facts and the results about Lipschitz
geometry that are needed to understand the proofs, providing references.
