Answer:
When we're babies.
Explanation:
When you're born, all of your bones are almost completely formed out of cartilage, and you have approximately 300 of them. Over time, your bones begin to fuse together and solidify into pure bone. When your born about half of your bones are solid cartilage and the other half is a mixture, that usually applies to your bigger bones like the bones you have in your legs as they have to be at least partly solidified enough for you to function
It would have to be refrigeration.
