See the fossilised footprints of the first bird and discover how remains of organisms have been preserved for 150 million years. Material processes - Classifying materials - Rocks Learning Points Fossils form when the remains or marks left by living things become trapped or buried. A Twig Curriculum Film. Delivering key learning points. Get straight to the facts in just three minutes – directly linked to core learning, Twig's curriculum films will fit neatly into your lesson plans.