Amber is fossilized tree resin (not sap), and it has been prized for its color and natural beauty since the Neolithic period. Amber has long been prized as a gemstone, and it is now used to create a range of beautiful products. Amber is used as a component in fragrances, as a folk medicine therapeutic agent, and as jewelry. Modern scientists are studying how the chemical components of amber interact with living cells. Amber has been used for many centuries in various forms of art, from jewelry to sculpture. In science, amber is used as a medium for microorganisms that grow within it; these include plants and animals. The inside of amber contains chemicals that kill or repel insects who try to eat it, and this property has been used to good effect by naturalists when cleaning specimens in museum collections. A study conducted in 2015 by researchers at the University of Aberdeen found evidence that ancient Celtic priests wore amber beads as a sign of status. The study also revealed traces of pollen, seeds, insect legs, and feathers in the beads, which showed that people had used them as jewelry for decorative purposes as well as wealth. This shows that amber was widely used in Europe around 2,000 years ago. In modern society, amber is used primarily as a material for jewelry. It is known as "the stone for eternity" because of this tradition of using it as an ornament. Amber is also used as a home decor item.