Timeless Child's regenerations

Following the young girl and her friend playing on the top of a cliff, an accident occurred, in which the girl fell off the edge of the cliff and dropped a distance onto the ground below, causing the child's death. A few moments later the girl started to glow with regeneration energy, the very first of many regenerations on Gallifrey, witnessed by her adoptive mother Tecteun. The regeneration caused the child to change appearance, and she now had the appearance of a slightly older, asian-looking girl.

This inspired Tecteun to want to study the effects of regeneration in order to transplant it into herself. Although, the experiments would take ages to succeed, driving Tecteun mad in her desperation to learn the secret, and the child would endure many more forced regenerations, turning her into a younger, caucasian girl, then into an asian-looking boy, then into a slightly older, caucasian boy, then into a young, teenaged, indian-looking girl before finally turning her into a teenaged, young black boy, cracking the secret in the process, and regenerating into a man. (TV: The Timeless Children)