TikTok is one of the fastest-growing apps in the world and has now been downloaded more than two billion times. It is most famous for lip-syncing teenagers and out-of-control pets, but its phenomenal growth means it is starting to change the world - and nowhere is that clearer than in the US presidential election.Donald Trump may not be a fan, but his supporters and Joe Biden's are now fighting for the future of their country on TikTok. With just over a week to go until America decides, Sophia Smith-Galer delves into the crazy world of TikTok. She meets its breakout stars - from the Republican Girls to the Minnesota state senator who uses it to get out the Democrat vote.How is TikTok changing US politics, and what influence will it have on who the White House's next resident will be?