Board Thread:Naruto Discussions/@comment-26320097-20150423120614/@comment-3965545-20150625094116

it was either an umbilical cord or a hair. If it was a hair then it was definitely Karin's if it was an umbilical then there is a chance it was Sarada's or Sasuke's. but I do believe it was a hair because an umbilical cord would not fit into that vial.