Ambre
It is a resin of tree hardened, consisted of sap, alcohols, which covers the bark. The trees produce this sap like protection against the diseases and the attack of insects. . After having exuded outside, the resin hardened in wet sediments, like clay and sand. It is at the bottoms of the lagoons or deltas of river that was preserved during millenia.
The chemical composition of the resin which acted like dessicant and antibiotic grabbed the animals like insects (i.e. mosquitos, flies, spiders, ants and its eggs and emergent larvae) but still of the lizards and frogs. They remained imprisoned in the resin, they were kept and preserved like fossil inclusions dehydrated. They were maintained in their cellular structure this is why we still can take fragments of ADN today