Of course slime has always existed but this YouTube slime movement is way bigger than anything that was on Nickelodeon. I don't think you realise the magnitude.
My daughter? Had me buy a book for her from some girl that she said is on YouTube who makes slime (the book is about slime), she wants glue and other items for the mixture almost constantly, and if she sees a container of slime at Target that looks cool, that's the toy she wants over anything else.
It'd be one thing if that was just her niche, but damn, her friends are all about it too. It is kind of insane.