National Geographic has an amazing story about the discovery of a 100 million year old bird wing preserved in Burmese amber. The amber dates to the mid-Cretaceous. There's bone, soft tissue, and feathers and it's very similar to modern birds. The tiny pair of wings have been nicknamed "Angel", because it was originally intended to be used in a pendant called "Angel's Wings". A study of the mummified wings was published in the June 28th issue of Nature Communications.
While the fact that many, if not nearly all, dinosaurs were feathered has been generally accepted since the 1990s, our knowledge of prehistoric plumage until now has come from feather imprints in carbonized compression fossils and individual feathers fossilized in amber.
But while feather imprints in compression fossils may show arrangement, they generally lack very fine detail and rarely preserve information on color, while individual feathers in amber cannot be associated with the animal they originally came from.