have been precipitated in polymer membranes with bicontinuous structures whereby the morphologies are dictated by the polymer membrane. The single crystals exhibit intricate, sponge-like morphologies, demonstrating that synthesis of single crystals with complex structure is not restricted to the realm of biomineralization. (F. C. Meldrum et al., August 16, Adv. Mater. 2002, 14, 1167-1169)