The big day has finally arrived, trainers.

Over the past few months, rumours and speculation about the arrival of Generation Two in Pokémon Go have reached absolute fever pitch.

It started last December when the baby Pokémon were added to the game, and since then the excitement (and frustration) has been mounting steadily.

Now, at last, the update people have been crying out for has been announced.

Right, so what exactly is being added to the game, and when?

We've broken down all the new additions and features, and everything we currently know about them from the press release, below.

80 new Pokémon

Image: niantic/mashable composite

In a nutshell, the main bulk of Generation Two — the Pokémon from the Johto region that originally appeared in the Gold and Silver Game Boy games — will start appearing in the wild later this week.

The trailer above shows people gleefully catching the likes of Hoppip, Marill, and Skarmony, which are just a handful of the 80 additional Pokémon confirmed in the press release sent to Mashable.

So, two main questions: 1) When exactly will these be in the game, and 2) Why only 80, when there are 100 Pokémon in Gen 2?

Well the press release doesn't give an exact date/time, but "later in the week" indicates we'll have them by Friday or Saturday at the latest (probably after this week's update has fully rolled out).

In regards to the 80 number, it's worth remembering that eight Gen 2 Pokémon (seven babies plus Togetic) are already in the game. There are also a whole new set of Gen 2 legendaries that we obviously won't be getting yet (we still don't have the Gen 1 legendaries, after all).

Even taking into account the eight existing Gen 2s and six legendaries, though, that still leaves seven Pokémon unaccounted for. Our best guess is that these are the likes of Unown and Wobbuffet — essentially the Gen 2 equivalents of Ditto, which may require special moves or additions that will need to be added over the coming weeks/months.

Two new berries

Image: niantic

This is pretty exciting.

To increase your options when capturing a Pokémon, Niantic are adding two brand new berries to the game: the Pinap Berry and the Nanab Berry.

The Nanab Berry slows down a Pokémon's movements to make it easier to catch, while the Pinap Berry — which is a bit of a game-changer, in our opinion — means the candy you receive for a Pokémon will be doubled if your next catch attempt is successful.

There's currently no word on the level these berries are unlocked at or how they're acquired (we're assuming they'll come out of Pokéstops like their Razz Berry cousins).

Evolution stones

Evolution items were first hinted at in the data mine of the January update, and they've now been officially confirmed.

Details are thin at this stage — we know for sure that these will be used to evolve certain Gen 1 Pokémon (like Onix and Seadra) into their new Gen 2 evolutions, but we don't know exactly how the stones will be acquired in the game.

Avatar customisation

What's the point in being the best like no one ever was if you can't look cool doing it, right?

Luckily, the latest update has taken into account our in-game avatars, too, who will soon be able to dress themselves in "a new selection of hats, shirts, pants, and other items".

These will be available from the in-game shop, according to the press release.

“Today is a momentous occasion for our team here at Niantic which has been hard at work to deliver these additional Pokémon and build upon the encounter and capture mechanics for our passionate global community of Trainers playing Pokémon Go,” Niantic founder and CEO John Hanke was quoted as saying.

“Pokémon Go is a live experience which we’ll be continuing to support and evolve in new and interesting ways for years to come with new gameplay features, in-game and live events, more Pokémon to discover and much more.”

It's officially time to get excited.

UPDATE: Feb. 15, 2017, 12:14 p.m. GMT An official update has been published on Pokémon Go Live that confirms Evolution items and new berries will be available from PokéStops, and that Pokémon may "react in new ways" when encountered in the wild.