Amber is in some ways the best preserving medium of fossil plants and animals known. The fossils are preserved in three dimensions, with great surface detail, and allow snapshots of interactions between animals - such as an ectoparasitic mite sucking the haemolymph of its victim, a swarm of nematodes parasitizing a beetle, acts of mating, and an ant queen carrying her domesticated honeydew provider. No other style of exceptional fossil preservation can compare.
The oldest ambers with included animal fossils date back to the Cretaceous (though now in 2012 there's a single Triassic case), with the best known occurrences being those from Lebanon, France, Burma and New Jersey (USA). This small collection contains examples from Burma. They are of earliest Cenomanian (a little less than 100 Ma) age and come from Main Khun, Tanai Township, Kachin State, Burma. Burmese amber was formed by a conifer, perhaps Metasequoia, in a tropical palaeoenvironment (Grimaldi et al 2002).