This story is a sequel to Celestia's Tiny Student

(Title changed from "Ponyville's Tiny Librarian" for reason pointed in this blog )

Twilight Sparkle is a one-kilogram pony the size of a large rat, shrunken by Princess Celestia following her entrance exam to the Celestia’s School for Gifted Unicorns to ensure that her power surges would not pose a danger to the ponies around her.

She’s spent thirteen years full of hard training at her new size, facing the life-threatening experiences that came with living in a world of giants. To survive those thirteen years of hardship and joy, of learning and adventure, and of pride and humility, Twilight has challenged herself to be stronger, to overcome any obstacle.

Now that tiny Twilight is on her way to Ponyville to oversee the preparations for the Summer Sun Celebration, how well will this miniature mare fare outside of the confines of the castle? How will the other Element Bearers react to her? How will Nightmare Moon react to the tiny unicorn? Is Twiny prepared to face Ponyville, and, more importantly, is Ponyville prepared to face her?

Credits:
Art cover - kc day

Top editors: (editing and rewritting for months, hope quality is to your liking).
Kydois
Georg

Nightmare Moon's sentences editor:
Bahatumay

Applejack accent editor:
Crimson Star (Chapter 1 - Applejack)
Rebel Brony
The Notebook is grounded

Pinkie sentence's editor:
Plump it UP

Other editors:
Hereward
tana1100
Lab (small editing from prologue to chapter 4)

Pre-reader:
Rated Ponystar

To celebrate the release of this sequel, I created a group called “Twinyverse” for all fans of this story where you can talk about it and track all side stories with ease.
The Twinyverse Group

In an Equestria without the Princesses or the guidance of the Elements of Harmony, Twilight Sparkle is a researcher on the cusp of her greatest discovery and simultaneous fall from grace while finding love at the same time.

Initially written for the May/June Twiluna contest. Proofreading and idea-seeding credit goes to Pearple Prose Rated Teen for language and implied sex/violence.

Look at your hand. Is it really there, or are you just imagining things? How are you able to know for sure that it's actually there. What if it was something small, unnoticeable, like a single skin cell out of place. But because of that one skin cell, you're now out of the loop of reality. Will you have ever known that that one cell was out of place, or will you just assume it's right where its always been? What about when another, and another cell becomes desynced from reality. You won't even feel yourself shifting ever so slightly, all you'll feel, is what you want to feel. You'll feel like those cells have always been there, and you won't even percieve yourself changing. It'll be reality. But not the true reality, your reality.

Join Discord, as he reveals the truth about reality to Twilight.

[I encourage everyone who likes this story to recommend it to friends and followers, it really helps a lot. If you disliked it, please leave a comment explaining why so I can grow as a writer. Thanks!]

Twilight loves her. She is the Princess, the beautiful, powerful, kind ruler of Equestria. But when the Princess denies her, Twilight vows to become stronger, to be better. Until one day, she will be so powerful that not even her mentor can ignore her any longer. One day, she would make Celestia love her back.

When filly Twilight asks Celestia to tell her a bedtime story, the Princess is not prepared for the many memories that float to the surface once she is asked this. She mainly remembers a small filly just like Twilight, who also asked for bedtime stories many years ago.

Banishment.
Such a powerful word with such a simple meaning. A word most ponies never hear in their life...
"Twilight Sparkle,"
A simple word meaning to be sent away as a form of punishment...
"You have been proven guilty,"
But I haven't done anything wrong, have I? Anything to deserve to be punished? Being framed? Is that a crime?
"You are banished from Equestria,"
Why would they all just give up on me? I know the truth, but they refuse to hear it. Why won't they just listen?
"You are required to leave at once."
Just listen.
Before war overtakes us all.

Featured-- 3/5/14
Give cover art respect where it is due, meaning this guy.

For a thousand years, the Code of Harmony has ruled Equestria, and the Code of Dissonance has sabotaged its works at every turn. Now the war for control over the land will come to a head, and one unicorn's decision may decide the fate of all.

For though she does not know it, Twilight Sparkle is the shining example of the Code of Harmony. Her teacher, Princess Celestia is Harmony's most powerful master and she knows her enemies are hatching a plan that threatens to cast down the Harmony of her throne and all she has sacrificed to create.

What she does not know is her foe seeks a new Apprentice to turn to his dark ways. A unicorn with seemingly limitless potential for magic, whose thirst for knowledge may yet lead her down a dark path, who is known to be such a faithful student of magic, eagerly seeking the truth no matter how forbidden it might be...

Sequel: Code of Harmony

This is a fic based on the Time Loop Files, the format of which was first codified by Innortal on fanfiction.net.
Here's a brief guide.
The basic idea is, one character (the Anchor, usually the main character of a fictional setting) is looping back to the very first moments of their parent series every time either they die or some kind of time limit expires. They of course end up monumentally stir crazy given enough time.
Eventually others start to loop as well.
The reset is not always perfect. Sometimes a loop's history will be different to the "prime" loop, or canonical plot.
"Crossover" or "Fusion" loops also occur, randomly. These can involve the home loopers having a guest, or the anchor for one universe spending time in another, or replacements of one character by another.
Vacation Loops are where the Anchor (or others) decide/s "buck it" and lets off steam by doing whatever comes to mind. There's little or no attempt to maintain the original timeline.

In addition, and particularly more recently, it should be known that this story has a collaborative element to it - people may submit loop ideas or loops, ideally at the Spacebattles thread (a link to the current version of which is on the Trope page), and they may become included.

There's two page image options, thanks to Filraen - the current page image has been edited by the original creator from this work of theirs.. The other one is here:
http://hourglass-vectors.deviantart.com/art/MLP-Loops-466030169