For the last 500 million years algae have shaped our environment by fixing CO2 via precipitation of minerals. This mineralization process takes place under strict biological control, giving rise to a variety of complex architectures with spectacular mineral morphologies. Among them are the highly ordered, mesoporous shells of single-celled dinoflagellates, such as Leonella granifera. Their shell is made of calcite that provides the organism with structural support and protection. The shell’s long-range morphological regularity is beyond the reach of current human technology and a paradigm example of regularity in biological systems. However, the biological mechanisms that control the intricate construction of this mineral are largely unknown.

Calcitic shell of L. granifera (left) and cryo-SEM image of the calcite shell crosssection (right)

Elucidating these processes is challenging, since it requires tracking transient, highly soluble inorganic precursor phases at the nanometer-scale. Recent developments in live fluorescent imaging and the cryo-preservation of cells make it possible to follow calcification processes with molecular resolution.