where did the did the 'body adventure' idea originate from?

I always see it at one point or another; a group of people shrink down to microscopic size in a ship and go inside the human body, having minutes to escape before they regrow to normal size. Its a fascinating idea, despite the overuse of it.

I read 'The Time Machine' and 'The Invisible Man' because I had seen so many references to these two books in media, and I was NOT disappointed! :3 is there a book, or a movie that this whole 'body adventure' thing came from? Even if it was just a theory devised by a notable person and not a tangible story, I'd still like to know its source.