Scientists have unearthed giant magnetic fossils, the remnants of microbes buried in 55-million-year-old sediment. The growth of these unusual structures during a period of massive global warming provides clues about how climate change might alter the behaviour of organisms. The new fossils are "unlike any magnetite crystal ever described", says Dirk Schumann of McGill University. Schumann and his colleagues found the fossils in sediment taken from a borehole in Ancora, New Jersey. The finding backs predictions that the ecology of the coastal oceans will change in unexpected ways as temperatures rise with current global warming.