ABSTRACT. – The cuttlefish’s inner shell, better known under the name “cuttlebone”, is a complex structure that has been studied by scientists since nearly two centuries. Indeed, this shell which is involved in tissue support and buoyancy regulation unites useful properties such as high mechanical resistance, porosity and permeability. Moreover, this ostensibly straight shell is unique in extant and known extinct cephalopods and thus of great interest to better understand the evolution of this mollusk group. However, despite various studies dedicated to the evolutionary history, the morphology, the microstructure, the composition and the functioning of this shell, a lot of open questions persist. Based on detailed pictures originating from adult and juvenile stages, this review aims to critically scrutinize data about the known structures of the Sepia officinalis shell and to describe its setting up during early-life stages in order to improve our understanding of the establishment of this elaborate structure.