Mew is a pink, bipedal Pokémon with mammalian features. It has a rounded, wide snout; triangular ears; and large, blue eyes. It has short arms with three-fingered paws and large hind paws with oval markings on the soles. Its tail is long and thin with an ovoid tip. Its fur is so fine and thin, it can only be seen under a microscope.

Mew has shown a playful, childish personality, showing signs of high intelligence, curiosity, shyness, playfulness, and even selflessness. It is said to have the DNA of every single Pokémon contained within its body. This causes many scientists to theorize that Mew is the ancestor of all Pokémon. It is an incredibly adaptable species, capable of levitation and teleportation. It can use almost all known moves, regardless of their types. It has also shown the rare power to transform into all known Pokémon. It is capable of making itself invisible at will, so it entirely avoids notice even if it approaches people. As seen on several occasions, it has the ability to create an orb of energy around itself for protection, which can come in many colors, such as green, yellow, and pink.

According to journals found in Kanto's Pokémon Mansion, Mr. Fuji is the one who discovered Mew deep in the jungle and coined its name. With other scientists, he managed to gather some of Mew's DNA and used it in his mansion to create a modified clone of it, aiming it to be the most powerful Pokémon of all, which resulted in the birth of the Legendary Pokémon . Since Mew can make itself invisible, very few people have seen it, leading some scientists to declare it extinct and most to assume it to be nothing, but a mirage. However, sightings of it are still being reported to this day, confirming its existence. Even though it's rarely seen, it will willingly show itself to a person who is pure of heart and has a strong desire to see it.

According to the Pokémon the Series-related radio drama, The Birth of Mewtwo, Mew was discovered by 's mother, Miyamoto, who registered its cry in a forest 20 years before the events of the series. It was worshiped for its protection by ancient people who created a song in its honor and believed it appeared once a year with the rising sun. It wasn't rediscovered until 18 years after Miyamoto met Mew by sunrise on the peak of a high mountain. As depicted in the episode In the Palms of our Hands! (JN134) it is capable of splitting itself up and transforming into more than one Pokémon at the same time. It was also shown to possess a strong rivalry with its clone, Mewtwo in Mewtwo Strikes Back (M01).

(Source: Bulbapedia)