This is the world's smallest working model train. How small is it, exactly? Well, it's a 1:35,200 scale model, and the whole deal measures a mere 1/8 inch x 1/4 inch.
It's all the work of a New Jersey model train enthusiast named David Smith, and he created it to go inside the model shop he's building as part of another model train set. Yes, it's a working model train set inside another working model train set. Consider my mind blown.