The preadolescent stage of growth and development begins at the age of what?

Preadolescence is a stage of human development following early childhood and prior to adolescence.[1] It generally ends with the beginning of puberty, but may also be defined as ending with the start of the teenage years.[2][3][4] For example, dictionary definitions generally designate it as 10-13 years.[5] It may also be defined as the period from 9-14 years.[6][7] One can also distinguish middle childhood and preadolescence[6] - middle childhood from approximately 5-8 years, as opposed to the time children are generally considered to reach preadolescence (age 9-14 years).[7]