The body can just do things. Always rebuilding.

Immune cells: hours
Small-intestine lining: 3-5 days
Stomach lining: 3-6 days
Taste-bud cells: 10 days
Skin epidermis: 1 month
Red blood cells: 120 days
Liver cells: 1 year
Fat cells: 10 years
Skeleton: 10 years
Brain neurons:…