Simply, nanoart is an art in nanometer scale. You can only see under electron microscope. You may see below as an example where photo is taken by microscope, showing different type of pollens.
The subject may be natural or synthetic. This is also an important category of art where art and science meet. A very good example is the boy and his atom.
The nanoart even can be in the needle eye;
Here the art is done in the eye of the needle. These art are also only visible through microscope.
If you are interested in this, one of the best websites is nanoart.com. This is a website founded by Chris Orfescu. https://crisorfescu.com/
Real as well as surrealist photos are also possible.
Here is also you may experience great photos from Willard Wigan