If you buy or are given a piece of amber containing an insect or plant, how do you know what you are looking at? Although there are many characteristics that can help to distinguish between the various groups of organisms, most of these are difficult to see in amber because the insect or plant is not in its natural resting state. Help is at hand. Andrew Ross, who is curator of fossil arthropods in the Department of Palaeontology at the Natural History Museum in London, has produced a little book about ways to identify the creatures and plants you are most likely to see captured in amber. Amber (Harvard University Press, $12.95) provides detailed keys to identification, so that you can easily recognize the lacewing (Neuroptera) shown above or the cypress twig (Thula), inset.