Princess Twilight Sparkle has always lived a busy life in Equestria, even before fully committing to her mission of understanding everything about the magic of friendship and earning her title she was always known for her passion for books and knowledge, not only about magic but also all kinds of topics, from the history of Equestria to the most random tidbits of knowledge that according to her, could point out to discovering lost in time secrets. Some of the information she found and read about seemed so strange or so silly she didn't even bother sharing it with others unless they were very interested on it, because as much as she wanted to delve deeper into such topics, real life with her friends and her duties as a princess easily took priority.

"Wait, you've heard about THAT?!" Her tone of voice revealed her excitement when Anon made one of those infrequent surprise visits and talked with her about the "mysteries" hidden within the bodies of ponies.

"I was so surprised when I stumbled upon that I thought it was some of the best fiction I've ever read, and just had to share it with my booklover pony friend" Anon smiled at the Princess, explaining how did he come upon that old incomplete text talking about how inside the body of a pony you would find more than the typical anatomy depicted in medical books, but if looking with enough detail, you would find pretty much another sentient world composed by sentient cells.

"Yep, the mythical cities." Twilight said with a look that Anon at this point could recognize. Not because they were super close friends, but because they shared the same interest in the pursuit of knowledge. It was a look that said that either Twilight knew that myth was true, or that she really wanted it to be true.

"You.. you know more about this?!" Anon exclaimed.

"Not much, but there are a couple of ancient apocrypha out there, from different times, that share a similar belief of what is within our bodies." Twilight said with a serious tone.

"But.. There's no way you can believe it, with everything you know and modern medicine.."

"That's true, but at the same time, there's so much we still don't know about our magic that this might be the key to finally find the answers, a deep exploration within our own bodies. I think those texts might be on to something." Twilight admitted with a sigh that seemed to indicate she felt a burden lifted out of her for saying such a thing out loud.

"I'm pretty sure you would have found something at this point, it just sounds so..unreal." Anon remained skeptical.

"Didn't humans believe something similar in the past too?" Twilight asked with curiosity and Anon explained to her that just like ponies, there were still unsolved questions about the human body and even if magic was unavailable to most, humans had a concept of soul to describe what makes them unique.

"Soul...what if our magic makes this soul appear like the mythical cities?" Twilight asked more to herself.

"I.. have no idea" Anon conceded.

"I do have one, but I would need your help. Are you busy?"

====================

Anon could barely believe Twilight's proposal but the passionate way she described it made it impossible to refuse. Basically she wanted Anon to shrink down and explore her own body in search of this mythical cities. She needed him because Anon was a capable wizard that could be able to survive at such a minuscule size, because a spell she knew to alter the size of other living beings didn't work on ponies, and because she feared other ponies would consider her crazy if she dared to talk about this with any of them. 

In the end, the way she talked about what this could mean for the understanding of magic and other secrets in Equestria was so vibrant and contagious that it didn't take her much to get your permission. Both Anon and the Princess blushed after she expressed her heartfelt gratitude, their bond strengthened just by being kindred souls that wanted to help each other reach a common goal.

"I can tell this means a lot to you, sorry my magic is not good enough to shrink you down and explore somepony else." Anon apologized awkwardly.

"Are you kidding? The fact that you're letting me do this is already amazing. Thanks again, and let me know when you're ready." Twilight answered shyly, but clearly she was beaming from the excitement of unprecedented research, research she would only be able to make thanks to Anon.

What happens next?