  We present an overview of both older and recent developments concerning scale
separation in string theory. We focus on parametric scale separation obtained
at the classical level in flux compactifications down to AdS vacua. We review
the scenarios that have been proposed to achieve a hierarchy of scales between
spacetime and the internal space, built from a low-dimensional perspective. We
then discuss how they have been understood to arise from proper
higher-dimensional descriptions. Eventually, limitations of these constructions
as well as Swampland and holographic arguments addressing the question of scale
separation in string theory are discussed. The purpose of the review is to draw
an accurate picture of the state of the art of the subject at the moment.
