The argonaut constructs its shell via physical self-organization and coordinated cell sensorial activity. Checa González, Antonio G. Linares Ordóñez, Fátima Grenier Romero, Cristian Griesshaber, Erika Rodríguez Navarro, Alejandro Schmahl, Wolfgang W. We acknowledge TESCAN and Carl Zeiss Microscopy GmbH for the acquisition and early processing of the images by FIB-SEM. This research was funded by projects CGL2017-85118-P (A.G.C., C.G.), PID2020- 116660GB-I00 (A.G.C., C.G., A.B.R.-N.) (Spanish Ministerio de Ciencia e Innovación), and B-RNM-265- UGR18 (A.G.C., C.G., A.B.R.-N.) (Junta de Andalucía), the Unidad Científica de Excelencia UCE-PP2016-05 (A.G.C., C.G., A.B.R.-N.) (University of Granada), and the Research Group RNM363 (A.G.C., C.G.) (Junta de Andalucía). Conceptualization: A.G.C.; methodology: A.G.C., F.L., A.B.R.-N., and E.G.; investigation and formal analysis: all authors; visualization: A.G.C., F.L.; writing – original draft: A.G.C.; writing – review & editing: F.L., C.G., E.G., A.B.R.-N., W.W.S. The shell of the cephalopod Argonauta consists of two layers of fibers that elongate perpendicular to the shell surfaces. Fibers have a high-Mg calcitic core sheathed by thin organic membranes (>100 nm) and configurate a polygonal network in cross section. Their evolution has been studied by serial sectioning with electron microscopy-associated techniques. During growth, fibers with small cross-sectional areas shrink, whereas those with large sections widen. It is proposed that fibers evolve as an emulsion between the fluid precursors of both the mineral and organic phases. When polygons reach big cross-sectional areas, they become subdivided by new membranes. To explain both the continuation of the pattern and the subdivision process, the living cells from the mineralizing tissue must perform contact recognition of the previously formed pattern and subsequent secretion at sub-micron scale. Accordingly, the fabrication of the argonaut shell proceeds by physical self-organization together with direct cellular activity. 2021-11-26T11:34:31Z 2021-11-26T11:34:31Z 2021-11-19 journal article Checa, A. G., Linares, F., Grenier, C., Griesshaber, E., Rodríguez-Navarro, A. B., & Schmahl, W. W. (2021). The argonaut constructs its shell via physical self-organization and coordinated cell sensorial activity. Iscience, 24(11), 103288. [https://doi.org/10.1016/j.isci.2021.103288] http://hdl.handle.net/10481/71783 10.1016/j.isci.2021.103288 eng http://creativecommons.org/licenses/by-nc-nd/3.0/es/ open access Atribución-NoComercial-SinDerivadas 3.0 España Elsevier