u/MasterLibrarian97

I’m about to turn 26 in few monts ; I think that at 25 we leave a first phase of youth, but we remain young until around 35-39, It depends on the individual.

Then comes the 40–45 transition ; i suppose that mature age is around 45 ? And old age around 65... What do you think ?

Of course, i am referring to biological and "visual" youth. You can very well have much more energy at 55 than at 25 or 30.