Tree of Life (Winx Club)

The Tree of Life holds the positive and negative balance of magic and initially grew in the Pixie Village, till the Pixies seemingly moved their village somewhere still near the Tree, from where they, along with Ninfea, guard it. Inside of it flows all the magic of the Magic Dimension, containing both positive and negative magic which coexist in harmony, and the tree glows and grows thanks to this balance between the positive and negative energy within it. Each branch corresponds to a world, and each leaf to a fairy.

Seasons
It first appears in Season 2 as a flower-like plant from which the pixies are born. Icy froze it and the plant got sick. Sometime after, the pixies asked Flora to help, but she was afraid that if she makes a mistake, she could accidentally kill the plant and destroy the pixie race from existence, but with help and aid of Helia, Flora managed to heal the plant and save the pixies.
 * -|Season 2=

The Tree of Life was shown in the second episode of Season 4 this time as a real tree. One of its branches corresponds to Earth, and was empty for a long time, with only one leaf remaining, standing for the last fairy on Earth, Roxy. When the Winx defeated the Wizards of the Black Circle in the episode Attack of the Wizards, new leaves started growing again on it showing that Earth was ready to welcome new fairies.
 * -|Season 4=

It was only seen in the "Legendary Duel", after Aisha defeated the Gloomy Wood Trolls and saved the Pixies.
 * -|Season 6=

Movies
The Tree appears again in the second movie, where it is show that half of the Tree contains positive energy, with leaves and flowers standing for Fairies, and the other half contains negative energy, with curled branches.
 * -|Magical Adventure=

PopPixie
In PopPixie, the Tree of Life is an ancient magical tree which supplies all the magical power to Pixieville.

The Pixies are responsible for the safety of the Tree of Life. The protective energy of the Tree of Life, which feeds the Magical Barrier, defends the city from external threats.

The Tree of Life is covered with MagicPops, magical globes that contain positive energy which look like sparkling enchanted dust.

When a Pixie uses its Talent for a good purpose, to serve the well-being of the community, it receives a MagicPop from the Tree of Life. Discovering their talents and obtaining the MagicPop is a special moment in the life of Pixies and an important moment of their growth as they discover their positive qualities.

Trivia

 * In Season 2, it is called the "Flower of Life" instead.
 * As stated in Season 2 by Ninfea, Pixies are born from the Tree of Life. However, in PopPixie, there exist parents, siblings and cousin for Pixies. This is probably caused through a mistake from the developers.