experimental features?

Hello,
By using Bing regularly, I see interesting features passing, such as "cards" for certain animals, themes for the top of the search engine, particular layouts for recipes or castles in particular, improvements in visibility, all of them. these features are GREAT and INTERESTING, but they just don't hold up ... What do they have? They never stay, they leave, come back, without my knowing why! It's very annoying! 🙂