Normally, only the hard parts of animals and plants - shell, bone, teeth and wood - are preserved as fossils. However, every now and then conditions permit the preservation of soft parts and create treasure houses of information for palaeontologists. Sometimes, completely soft creatures such as jellyfish or worms are discovered and occasionally detail such as feathers, skin texture or (rarely) original colour is found, giving shape to creatures otherwise known only from skeletons or carapaces. In some cases, the fossils preserve details so fine - individual muscle fibres, for instance - they can only be seen with an electron microscope. Preservation of this quality is referred to as 'the Medusa effect'.
Fossil hunting is enjoyed by amateurs and professionals alike. In fact, palaeontology is one of the few sciences where amateurs have made - and continue to make - important new discoveries.