Amber is a fossil resin, produced by conifers. It emerges from trees as defence against damage and while still soft and sticky can catch and enclose insects. At a later stage, once the volatile components have been lost from the resin, and after millions of years and depending on the sediment, it becomes amber. Insects are the most common organisms found in amber and usually, except for having entirely dried up, they remain well preserved. Plants, spiders, crustaceans, snails, mammal hair, feathers, lizards and even frogs have all been found in amber.Amber sediments can vary in age from the Lower Cretaceous to the Holocene. The best known source of amber is the Baltic coast. The conifer forest in this region flooded in a marine event in the early Oligocene. Marine sediment buried the trees and the amber they contained. The amber subsequently was released by erosion.