Tiny little details and micro-worlds belong here. Also, if you have a photo taken through the microscope you may put it here.
Remember, macro is something shot in 1:1 mode, meaning closest you can get if you have macro lens at all. It's not enough to shoot in "macro" mode, or with macro lens. If you move farther away, that may be a close-up and it's not for this category.
Also, playing with water droplets at home is not nature photography.