I was luckier than I realized when my first two girlfriends had big tits. They both had what I learned were called “inverted” nipples, and that they’re actually rare. An inverted nipple is one that is folded in upon itself, points inward instead of outward, so it’s flat. Sometimes only one boob has an inverted nipple, and it can be either one, but my two girlfriends had both of theirs recessed. That didn’t mean much to me at the time. I just thought they were an example of the amazing variations that womens’ bodies can have. But I also concluded that all big boobs have them, and that’s not true. In my experience at that time, most skinny women had small breasts but long, sensitive nipples, so it made sense that chubbier babes with heavy boobs had the opposite. My first girlfriend was definitely a plumper and her boobs were big and fat and had wide, pale areoles and just slits for nipples. Even though her nipples looked so different they still turned me on, especially since they didn’t stay that way when they got stimulated. In fact, one reason I was so surprised to learn that her nipples were normally inverted is because the reason I was so attracted to her - why we met - is because I could see the location and shape of her nipples through her top. Turns out that was because they got cold which stimulated them. I watched her spend several minutes leaning over some freezer compartments at the grocery store and that made them “pop” (and so did my dick.) A woman has to have VERY big nipples to show through a bra and blouse so you can imagine my surprise when I finally got her topless and saw her nipples were flat folded slits instead of thick teats. But even though I was hoping to see them thimble sized and protruding I wasn’t disappointed. They still turned me on. There was something fleshy and sexy about them that still made me want to lick and suck them. And licked them and sucked them I did, and to my surprise again the slits opened up and long, wide teats emerged. My licking and sucking stimulated them just like the cold air did in the grocery store, and they popped again (and so did I after just a few minutes.) My second girlfriend wasn’t as chubby as the first one but she still had big boobs but they were firmer and had more shape. And they had inverted nipples too but instead of looking like folded in slits they looked more like craters. They were round instead of slotted and I could see down into them. I could see big pores which were her milk ducts. Again, her having different looking nipples didn’t bother me. In fact, seeing her milk ducts so clearly made me hard. Besides, I had already concluded that big boobs have flat nipples, unlike smaller, perkier breasts, so it was okay. I licked and sucked hers too, and also probed the tip of my tongue down into them to touch the milk ducts. That really felt good to her. She said she’d never felt anything like it. It made her horny. It also made her teats pop out too, just like my first girlfriend’s. But her teats were larger in diameter and not as long, and had big voluptuous ducts. I could clearly see each individual one and that they were porous. She got so turned on feeling and seeing her nipples so stimulated - and that I was so stimulated too - that she began squeezing them with her fingers to increase her pleasure. After only a few seconds clear liquid began to come out of them and then it turned white. It was milk. I was rock hard by then anyway, seeing her teats emerge and looking so pregnant, but that put me into another gear. I licked the milk as it dribbled out like a starving calf, until I finally HAD to come. I've had a thing for inverted nipples ever since.