This was written a long time ago when I wasn't the best at writing. Since then, I have rehashed and rewritten this with new science and new writing techniques.

Eevee:

Now, let us get started with the beginning of an Eeveelutions life, the egg.

Eeveelutions are remarkably good at producing offspring. It takes about 2-4 weeks from conception for an Eevee to hatch. In the 2-4 weeks that an Eevee develops, the Eevee will live in the mother's womb for about 1-2 weeks. They will finish the rest of the pregnancy in the egg. (is it still a pregnancy if they are in an egg?) The reason why an Eevee lives in the mother's womb for so long is not entirely explicit, though this is when the outer and inner shell of the egg is grown. By the time an Eevee is ready to hatch, the development of its brain would be enough for the Eevee to understand its surroundings. From here, the Eevee's brain would start to develop over the next 5 to 6 years along with its body. These years are the developmental years of an Eevees life where its mind and body prepare for puberty and all the stresses coming along with it. One of the first phases that an Eevee goes into is a phase where its mind matures rapidly. The growth of its mind is so fast that an Eevee can learn to speak fluently in a language by 2-3 years old. And by the age of 5 to 6, the Eevee will start to have ideologies and beliefs of its own. The Eevee body will have its phases that are preparing the Eevee for evolution which occurs during puberty. An Eevee evolution is an ultimate process that the Eevee can't perform before puberty. It will cause severe harm to its body, possibly stunting the Eevee growth.

puberty:

During Eevee's adolescence, several things will start to happen. One of those is the start of a female Eevee's heat cycle. The Heat season begins in the late spring and ends in the early fall. When this starts, and the female Eevee is in puberty, she will have a chance of getting heat. The typical female Eevee's heat cycle acts differently from other animals. Every two weeks, an Eevee is supposed to go into heat, but this is not the only thing that happens. The Eevee will also have constant hormonal changes during this time.

Everything said about Eevee's heat is constant throughout all the Eeveelutions unless stated so.

The other thing that will start to happen in puberty is evolution. Evolution is the Deciding Factor in what Eeveelution an Eevee is going to become. Amongst all the cultures that Eeveelutions are a part of (especially the cultures that Eeveelutions create.), it's a widely important thing. And even for an Eevee's body.

Jolteon:

It is impressive to see how evolution has created a fox that can harness the power of electricity, but how does this happen? Well, it starts at an organ located right beside the liver. This organ is responsible for generating electricity, which also produces heat as a by-product. The organ generation electricity by taking the nutrients from the cells that create energy and ionizing them using a 5%~ concentrated sodium. The ionization of the nutrients happens when the 5%~ reduced sodium and the nutrients get propelled around the organ.

The organ, which looks like a bigger heart, can pump the nutrients and concentrated sodium at a speed of 200 to 250BPM. At those speeds, the nutrients get ionized and create electricity. The electricity gets sent around their body to get used in whatever way they want.

In some extreme cases, a jolteon's body might create electricity and send it throughout its body to warm itself up. Though it only does this in extreme scenarios since it can be more damaging than creating heat ordinarily.

Espeon:

Espeon.

They are one of the most luxurious and elegant evolution in the Eevee family. With the power of royalty and class, espeon tend to be the leader or richest of any civilization. Couple that with their extraordinary psychic ability and espeon start to rule over their species. Even though espeon tent to be one of the more popular evolutions amongst its species, their numbers are fewer than any other Eeveelution. That is because becoming an espeon takes time, patience, effort, and a tiny bit of luck. Sunrise to sunset is the only window for an Eevee to convert into an espeon, and most Eevee's have to be well adjusted in their physical and mental attributes for it to happen. And even then, half of the Eevee population won't even get a chance to evolve into an espeon.

Why this happens is because there are more factors involved with the evolutions than just the sun. Yes, the sun is needed for an Eevee to become an espeon, but they also need radiation. Any type can trigger this evolution, but gamma radiation is preferred. Why an Eevee needs radiation is because of the gem that forms on an espeon's head. This gem is the reason why an espeon can do what it can do. The gemstone forms by a liquid that only an espeon's body can. The liquid is highly radioactive, admitting a new undiscovered radiation particle called Blank. Blank radiation is how the gem works, how the psychic powers happen.

For an Eevee to evolve into an espeon, it will need to take a large amount of radiation. What the radiation will do to the Eevee is