Whether big, small, perky or lop-sided, there's no denying that owning boobs can takes its toll (bra-sizes, cancer, etc). While it might not be Breast Cancer Awareness day, we figure that your mammaries still could use a little more appreciation. Below is a list of surprising facts that you probably didn't know about breasts:

There are only four types of nipples

According to Jezebel writer Tracie Egan Morrissey, common variations include "normal" that stick out a few millimeters from the areola; "flat" that only protrude when they're stimulated or when temperatures change; "puffy" that have a raised areola; and "inverted" nipples which are essentially turned inward. But if the nipple has only recently turned inward, get it checked by a doctor.

The left boob tends to be larger

According to author Jenna Pincott, it's perfectly normal for women to have one breast that's larger than the other, and 65 percent say it's usually the left one. No one knows for sure why, but theories include immune hypersensitivity which is higher on the left side of the body, or that women tend to prefer to nurse on their left side (leaving their right hand free) which results in that side producing more milk.

The size always fluctuates

Many women experience breast growth during PMS when the body has higher levels of the hormones progesterone and prolactin which can cause swelling. Some sex experts state that breasts can even swell by up to 25 percent during moments of intense sexual arousal.

They make the perfect food

According to the World Health Organization, breast milk contains antibodies that help babies fight infections and diseases while being easy enough for them to digest, making it the "perfect food" for babies.This is made by cells in the breast called "alveoli," which produce milk in response to the hormone prolactin that gets released when suckled.

When it comes to milk, size doesn't matter

According to board certified lactation consultant Debbi Donovan, "Larger breasts have a higher proportion of fatty tissue, compared to glandular tissue, but this has no effect on the amount of milk you're able to produce." Women with larger breasts may experience greater difficulties mainly from finding the right positioning for the baby.

Humans are the only primates with "permanent" boobs

According to writer Carole Jahme (who holds a master's degree in evolutionary psychology), humans are the only mammals whose breasts remain full after childbirth. Theories include breasts being a signal of "residual reproductive value," or that women's breasts became round after the female ancestors of humans stood upright.

The largest natural breasts are a 102ZZZ

Annie Hawkins-Turner is the current Guinness World Record holder for the largest natural breasts. Her chest measures 70 inches over the nipples and around her back. That amounts to about 3.5 feet of cleavage, with each side weighing in at whopping 56 pounds.

Breast orgasms exist

Studies have found that women can indeed orgasm through nipple stimulation. One study of 213 women found that 29 percent said they had experienced a "breast orgasm" at one point or another. Another 2011 study discovered that nipple self-stimulation led to activation in the brain's genital sensory cortex, a result the researchers called "unexpected."