The eggshell is a critical barrier against mechanical stresses and microbial penetration. Its integrity is essential to maintain the hygienic quality of this basic human food and to limit the number of downgraded eggs. The eggshell is made of 95% mineral phase (calcium carbonate on calcite form) and an organic matrix (3.5%) mostly containing proteins. Eggshell formation arises from an extra-cellular biomineralization process. We describe in this review, the latest advances in the formation of the eggshell, which takes place in a fluid that contains eggshell precursors and involves a transient phase of amorphous calcium carbonate (ACC). We also describe recent insight on the identification of transient amorphous calcium carbonate explaining this rapid mineralization process. We also report on the advances on the function of shell matrix proteins to interact with mineral, thus determining the crystal polymorph, the first event of nucleation and the final texture of the shell and consequently its resulting mechanical properties. The role of vesicular transport to provide stabilized ACC in chicken uterine fluid where mineralization takes place was also demonstrated recently. These extra-cellular vesicles play a crucial role in eggshell mineralization, in which annexins transfer calcium into vesicles and carbonic anhydrase 4 catalyzes the formation of HCO3-, for accumulation of ACC in vesicles. ACC is stabilized by ovalbumin and/or lysozyme or additional proteins identified in vesicles in this study. Finally, EDIL3 and MFGE8 are proposed to guide EVs to the mineralization site.