Skin is a living, metabolically active organ. Every day, it must produce new cells, repair damage, maintain hydration, regulate inflammation, and protect the body from the outside world. When we are young, these processes generally happen efficiently. As we age, they gradually become slower and less coordinated.
Most people begin experiencing subtle biological changes in their skin during their 20s. That does not mean everyone will suddenly develop wrinkles at 25. It means the systems responsible for renewal and repair are no longer operating at their childhood pace.
Genetics, hormones, health, nutrition, stress, skincare habits, and sun exposure all influence how quickly those changes become visible.