As it turns out, this story has a similarity to 'I'm His Favorite! Me!' by Madrigal-in-training. Although it was purely coincidental, I have been told to give him credit. Please note that other than the basic idea, I have no affiliation with that story or its author.
And as always, I do not own Harry Potter.
One year ago...
It was midnight, and ten-year-old Harry Potter sat in the Cupboard Under the Stairs, reading the only book he owned, The Language of Plants. He had to read it in the dead of night, so his Aunt and Uncle wouldn't know. It was a very interesting book. It was about what all the names of the flowers and plants meant. It was a rather large book too, at least three hundred pages. On each page there was the name of the flower or plant, and what the name meant. Characteristics of the plant were stated, along with a picture. The pictures were drawings, not photos, and Harry loved them.
Harry had had the book ever since he had found it in the basement when he was around eight years old. He had been cleaning, when he stumbled upon the book. He had flipped open to the front page, and there, written on it, in a spidery script, was 'To Lily - May you always have Majesty, Honor, and Purity of Heart, just like your namesake'. Harry figured this had to have been his mum's book. He took it, and hid it under a loose floor board in his cupboard, so no one could take it away from him.
He was almost done with the book. He didn't get much free time, so it was taking him longer then it should have. He worked hard to memorize what each plant meant, memorizing around five to eight a week. He was currently on the plant names that began with Ws, and would soon be on to the ones that began with Xs, Ys, and Zs...
Severus Snape sat behind his desk, waiting for the new students to arrive to class. As luck might have it, his first class of the day was with the first year Gryffindors and Slytherins, which of course meant him having to look at Harry Potter, the Boy-Who-Lived. He looked just like his father, except the boy had Lily's eyes. However, he had no doubt he was just like James. He was going to be an arrogant, ignorant, prat, just like his father was. But what if he's like Lily?
He would never get over Lily, no matter who she married, or if she were dead or alive. He would always love her, and he would always live with the fact that it was his fault she was dead, and died hating him. First he called her a Mudblood, then he got wrapped with jealousy and anger, and sold the Potters out to the Dark Lord. He would never forgive himself for what he did. He just wished he could apologize...
Just then, he heard the unmistakeable sound of children. He got up from his desk, and stood in front of it. He waited a few minutes, so everyone was waiting, and said his trademark 'Enter'.
The children filed in, the Gryffindors - and some of the Slytherins - looking at him nervously. He watched as everyone came in, and in the back of the line, he saw him, looking just like a mini James Potter, with his messy black hair and round glasses. But instead of hazel, his eyes shone a bright shade of emerald green.
He took a seat next to the Weasley and Granger, and started to get all his supplies out.
Snape took attendance, and paused at his name.
"Ah, yes," he said, just above a whisper, though everyone could here every word he said, "Harry Potter. Our new - celebrity."
The boy's face turned a shade of pink, and he looked down at his desk.
He than began his speech.
"You are here to learn the subtle science and exact art of potion-making," he began, "As there is little foolish wand-waving here, many of you will hardly believe this is magic. I don't expect you will really understand the beauty of the softly simmering cauldron with it's shimmering fumes, the delicate power of liquids that creep through human veins, bewitching the mind, ensnaring the senses... I can teach you how to bottle fame, brew glory, even put a stopper on death - if you aren't as big a bunch of dunderheads as I usually have to teach."
He noticed everyone was looking at him (though a lot seemed to not be listening), but one person was writing something down on a piece of parchment, not paying any attention at all. Just like his father. He thought. Or is he?
"Potter! What would I get if I added powdered root of asphodel to an infusion of wormwood?"
No one would know what it meant. Rarely anyone in the world knew about the language of plants. He remembered the day when he had given Lily that book. It had taken him forever to find it, and he had used up all of his savings for it.
He watched as the boy started thinking something in his head, and watched as his eyes widened, full of curiosity, and something else. Pity? Sorrow? He watched as he opened his mouth to answer the question, but in a way Severus would never have guessed.
"I bitterly regret Lily's death."