But that is the beauty of a microscope. It is not some “unrecognizable tech”. Seeing tiny things in detail is a basic skill many new civilisations can re-discover on their own. It doesn’t matter if it is our human descendants, smart octopuses or the silurians. They will be interested in seeing tiny things and thus they will construct their equivalent of microscopes.

The important thing is sign-posting. How will they know where to look?