Did you know that there are actual clinical categories of nipples? In fact, there are 8 different types! Who knew? The shape, appearance and size define what type of nipple category you fall in to. Personally, I just thought that nipples where nipples, however after finding this information out, I was very keen to know more!
'Normal' nipples protrude a few millimeters from the areola (the coloured circle that surrounds your nipple) naturally, but protrude further during temperature changes, arousal or stimulation.
Flat nipples are just that; flat. They don't stick out like 'normal' nipples do, instead, they blend into the areola. They do 'stick out' during arousal, temperature change and stimulation. They also have the ability to turn into 'normal' nipples when breast feeding.
These have the same characteristics as flat nipples, the only difference being that the areola is raised up off of the breast.
Inverted nipples are a result of the lactiferous ducts not getting properly stretched during puberty. They have a dimpled appearance and can also be drawn out after breast feeding. There are actually 3 types of inverted nipples:
Grade 1: These nipples can occasionally become 'hard' but mainly do through lightly squeezing them with your fingers. They can also maintain protrusion without disappearing and it is possible to breastfeed with this type.
Grade 2: These nipples can be pulled out, but not easily and once they do, they will retract back into the areola quickly. Breast feeding is possible, but can be tricky.
Grade 3: This type are severely retracted in the areola and can not be pulled through at all. The milk ducts tend to be constricted, making breast feeding somewhat impossible. Grade 3 inverted nipples, can be fixed through surgery.
This is when one nipple in inverted and the other isn't.
So despite some sounding a little more unusual than others and one category actually being called 'normal nipples', all 8 nipples are completely ordinary. In fact one study shows that 28-35% of women have nipples that don't protrude that well. Meaning that those 'abnormal' nipples, are actually more common than we thought.