Renesmee "Nessie" Carlie Cullen is the half-vampire, half-human daughter of Edward Cullen and Bella Swan, born on September 10, three days before Bella's nineteenth birthday in Breaking Dawn. Her name is derived from the amalgamation of the names of Bella's mother, Renée, and Edward's adoptive mother, Esme. Her middle name, Carlie, is a portmanteau of the names Carlisle, Edward's adoptive father, and Charlie, Bella's father. She has the same facial features and hair color as Edward, but has her grandfather, Charlie Swan's, curly hair, and brown eyes like Bella. Bella and Jacob describe her as being the most beautiful person in the world, even though she is so young. Her heart pumps blood, giving her a blush, and her pale skin glows in the sunlight. Her skin is warm and soft to the touch, but it is as strong as a vampire's. Renesmee can survive on either blood or human food, though she prefers blood, and she does not produce venom. Her special abilities are transmitting thoughts to others by touching their skin and penetrating shields, the opposite abilities of each of her parents. Renesmee rapidly grows both mentally and physically, able to speak only seven days after her birth, and by the end of Breaking Dawn she can read, run, hunt, and perform other tasks at advanced levels for her young age. Her intelligence stuns everyone - Bella and Edward especially - as she is able to understand what is happening around her when the Volturi arrive. Jacob Black nicknames her "Nessie" because he considers her full name to be a mouthful, though Bella strongly dislikes her child being nicknamed "after the Loch Ness Monster". However, by the book's end, all the characters adopt this shortened version. She will reach physical maturity after about seven years, when her physical appearance will be around seventeen, and then stop aging.
After Jacob Black imprints on Renesmee, Irina, a vampire from another coven, sees Renesmee and believes she is an "immortal child", a young child who had been bitten by a vampire. She informs the Volturi, as immortal children are not permitted to live, due to their unpredictable nature. Intent on killing Renesmee and all the Cullens, the Volturi travel to Forks. However, the Cullen family members gather witnesses from around the world to testify that they have seen her mature and grow, and so she is therefore not an immortal child. Alice brings another half-breed, 150-year-old Nahuel, who explains that half-breeds pose no danger to the vampires. Convinced that Renesmee is not a threat, the Volturi leave, and Renesmee and her family are left in peace.