The site of Jehol Biota in China is famous for stunning fossils which preserve soft tissue—skin, organs, feathers, and fur. These fossils offer rare insights into the evolution of characteristics like flight, but they need careful interpretation to understand what the soft tissue looked and behaved like in life, and how decomposition may have affected it.
source https://www.lifetechnology.com/blogs/life-technology-science-news/rare-fossilized-feathers-reveal-secrets-of-paleontology-hotspot-during-cretaceous-period