Many organisms have achieved, throughout the course of evolution, the ability to generate multifunctional and complex hierarchical structures combining organic and inorganic components. The outstanding fact is that simple organisms can build up biomaterials with unique mechanical properties that we cannot reproduce in our laboratories. Thus, mussels can produce and modify two minerals, calcite and aragonite, with different physical characteristics at variable pressure and temperatures. Combining both minerals with organic components, these marine invertebrates construct light, chemically stable, highly strong and resilient shells. A fundamental factor to explain our inability to accurately mimic these natural biomaterials is the insufficient knowledge about the interplay between biomineralization and the environment. The aim of this project is to study the structure of mussel shell layers living in different environments at water depths ranging from about 2,000 to 500 meters. Results will provide an insight on whether environmental parameters influence mechanical properties of biomaterials. In doing so, a fundamental knowledge of biomineralization processes will be gained for the future development of biomaterials for industrial and medical applications.