The eggshell provides convenient packaging for the transportation of the egg contents. Since the shell is fragile, it must be handled and transported with care. Cracked and damaged eggs lead to financial losses and pose a food safety risk. A greater understanding of the eggshell and its formation will allow breeders to select for hens that produce eggs with high-quality shells. This chapter describes the structure of the eggshell and introduces to our knowledge some of the advances about its composition and properties, which have resulted from the application of new molecular techniques, including proteomic and transcriptomic approaches. Where possible it suggests how these advances may allow us to address the major challenges in this area and contribute to sustainable egg production.