Did you know that the carboniferous era had bugs that were huge because there was more oxygen in the atmosphere, how about we get stuff like scorpions or something, put it in a giant terrarium, and hook that up to oxygen tanks, and breed for bigger and bigger offspring until they are bigger than theyve ever been and a human would probably be able to go into the terrarium for short periods, but you would probably not want to with a giant scorpion in there