Dad, how many kinds of breasts are there

A young man asks his father, “Dad, how many kinds of breasts are there?”
The father, surprised, answers:

“Well, son, there are three kinds of breasts.
In her twenties, a woman’s breasts are like melons, round and firm.
In her thirties to forties, they are like pears, still nice but hanging a bit.
After fifty, they are like onions.”
“Onions?”
“Yes, see them and they make you cry.”