We all have nipples, those delightful little nubs. For many of us, they're actually what's called a secondary erogenous zone, especially for women, which means that stimulating them can send pleasurable feelings right down to the genitals. Even so, some of us are very sensitive and others find their nipples are an absolute no-go zone. Wherever you find yourself on the spectrum, we believe these curious nipple facts will thrill you. (Read about other, lesser-known erogenous zones in The 6 Most Underrated Erogenous Zones.)

Your Nipples Are Perfect

No two nipples are alike. That means that the two nipples on your body may not be a mirror image of each other. This is normal.

The larger outer ring is your areola. For some women, the areola is light pink. For others, it can be darker and range from red to brown. For some women the areola becomes darker when they’re sexually excited. As a result, some cultures have even been known to paint their nipples to darken them in the hope of inspiring passion in their mates.

Email Newsletter

Join thousands receiving hot new sex related articles, goodies, and great deals.

Within the areola there can be little bumps. These bumps are the product of your Montgomery glands. These glands produce a protective, white, oily lubricant for the skin. This is also normal. Don’t squeeze those little bumps; they are there for a reason and opening them up can cause infection.

Females can grow hairs around their nipples. Our entire bodies are covered in fine, often almost invisible hair and sometimes a woman will have darker hairs that look almost like little eye lashes on the outer edge of the areola. These little hairs are more proof that you are normal.

Read: Squeeze Box: A Guide to Heavenly Breast Play

Got Milk?

There are two features that are unique to mammals: our hair and our milk producing breasts. The scientific term for having nipples is mammillated.

Each nipple has about 15 to 20 tiny openings. Some connect to milk ducts and some to the Montgomery glands I mentioned. The little whitish bumps you're seeing let you know where some of these openings are.

Other animals, like goats and cows, have one reservoir called an udder. The milk discharges through an opening in the udder called a teat. Still more curious is the platypus. A platypus does not have nipples or teats. Her milk is secreted out of two round patches of skin on her belly. Weird, huh?

Headlights On

Erect nipples always draw our attention, although it is a misconception that erect nipples are an indication that a woman is sexually aroused. (In other words, just because she’s got erect nipples doesn’t necessarily mean she’s raring to go!) Nipples become erect for many reasons, some of which are not sexual in nature, like if you are cold, or if they get sensation from your clothing rubbing on them. And sometimes a woman’s nipples may not be erect even when she is sexually excited.

Innie vs. Outie

Inverted nipples are fairly common. Anywhere from 10 to 20 percent of all women have them. An inverted nipple is caused by shorter-than-usual milk-bearing ducts in the breast. Those ducts are attached to the nipple and, in these cases, prevent the nipple itself from projecting. So the nipple may lie flat or even push in a little rather than projecting out. Inverted nipples don’t pose any health risk, although they may be an obstacle to new mothers as they breast-feed.

The easiest way to check whether your nipples are inverted is to gently pinch behind one, around the edges of the areola. If the nipple protrudes, it is not inverted. If your nipple is inverted it will actually retract into the breast. If you have inverted nipples and are interested in correcting it, there are solutions. Gently rolling the nipple may do the trick. For pregnant women who need to correct inverted nipples for breastfeeding, check out a maternity shop for disks that attach to the nipples and are designed to be worn inside a bra. This simple device gently stretches the tissue and encourages the nipple to stand outward.

Evolutionary Awesomeness (or Trickery?)

Human females are the only mammals that develop breasts and nipples that remain full and prominent, despite the fact that they are not lactating. Every other mammal only experiences prominent development during pregnancy and lactation.

Scientists speculate that the human female’s full breasts and erect nipples are a product of evolutionary development as a species. For other mammals, large breasts would be a sign that the female is lactating and not ovulating, and is therefore unavailable for procreation. Human females have developed ways of disguising when they are and are not fertile in order to confuse male mates and appear to be sexually desirable even when they are not ovulating. But we're also one of the few species that has sex just for fun! (Did you know that humans also have a hidden erogenous zone? Find out where it is in Your Hidden Erogenous Zone.)

Triple Nipple

Every now and then, you'll come across someone with an extra nipple - it's not that uncommon! These "supernumerary" nipples are common in many species, including primates, rodents and ruminants. Guys have extra nipples more often than females; 1 in 18 males and 1 in about 50 females have extra nipples. And a very select numbers of people have as many five or six nipples. Extra nipples usually run down the abdomen, along the milk line, but they have also been found on other locations, like on a person’s foot.

Whether they're big and bouncy or cute and pert, breasts - and their nipples - have a lot in common. But they're also all a little bit different, and a little unique. That means you'll have a little exploring to do, both with yourself, and with any new partner.

Do you need ideas for your next steamy scene? Take our quiz to get a personalized scene built just for you!

If you're just tipping your toe into the world of BDSM, you may be unsure where to even start when it comes to planning out a scene.

We made this quiz to provide you with your next, or first, BDSM scene based on your own tastes and desires!