The cover shows a scanning electron micrograph of vaterite crystals formed by the sea squirt Herdmania momus. These are the largest single crystals of vaterite ever observed, including biogenic, geologic or synthetic vaterite. Flat crystal faces are uncommon in biogenic crystals, but these crystals are clearly hexagonal pyramids. Pokroy et al. show that these crystals have smooth fracture surfaces; thus, they most likely formed ion-by-ion, rather than by attachment of particles. Narrowly distributed orientations and lack of organics at crystal interfaces suggest a new mechanism of biomineral crystal growth, perhaps spherulitic growth from solution. Article link.