One possibility could be that the Molecule Man's powers somehow disrupt the magic in the Harry Potter universe. Maybe he accidentally alters the molecular structure of Hogwarts, causing chaos among the students and teachers. Harry and his friends would then have to figure out how to reverse the changes and send the Molecule Man back to his own dimension.
The main antagonist could be an evil version of the Molecule Man. Maybe in his own dimension, he was corrupted by power and when he enters the Harry Potter universe, he wants to take over there as well. He would use his molecular manipulation powers to create all sorts of disasters, like turning the Forbidden Forest into a deadly, mutated place. Harry and his friends, along with the good - natured Molecule Man, would have to fight against this evil version.
One example could be a story where a single molecule is found in outer space that has the ability to terraform planets on its own. Another could be a scenario where a single molecule is used as a weapon that can dissolve any material it comes into contact with.
Single molecule science fiction could be about the potential of a single molecule having extraordinary capabilities. For example, a single molecule that can power a small device indefinitely. It might also involve the idea of a molecule being sentient or having the ability to transform matter at a microscopic level.
Spider Man is a very down - to - earth hero despite his superpowers. He's relatable and has a great sense of humor. Loki is a god with a lot of pride and a mischievous streak. In a fanfiction, their personalities would clash when Loki looks down on Spider Man's 'simple' life. But they could blend as Loki might come to admire Spider Man's ability to find joy in the little things and his unwavering sense of justice. This could lead to Loki becoming a more sympathetic character as he spends time with Spider Man.
A water molecule might start its day in a large body of water like an ocean. It is constantly moving and interacting with other molecules. It could be part of a wave, crashing onto the shore. Then, as the sun comes out, some of it might evaporate and turn into vapor, rising up into the atmosphere.
I really like the fanfiction 'Iron Man and Loki: A Strange Bond'. It starts with Loki being stranded on Earth and Iron Man being the first to encounter him. Instead of immediately fighting, they start to understand each other's motives. It shows a different side of both characters. There's also 'When Iron Man Meets Loki's Magic' which explores how Iron Man's high - tech gadgets react to Loki's magic, creating some really cool and unexpected scenarios.
A first person water molecule story could be about the journey of a water molecule. Maybe it starts in a cloud, feeling the coolness and the company of other molecules. Then it falls as rain, experiencing the rush through the air.