I was stunned by a recent image obtained in our fluorescent microscope staining discrete parts of the cellular surface of membranes and wondered (and calculated) how many molecules are needed to make a visible staining. the molecule I used was approximately 20 Angström (2 nm) long - the surface of the cell maybe 100 microm2 and the number of molecules was 602000000000000. Then I saw a picture taken from space facing the earth illuminated by road lighting (see image from Nasa). How many hundreds of thousands of street lights are needed to make a road visible from approx. 350 km above the earth surface - not so many as it appears. BTW, the lense of the camera is about at the same relative distance as the lense of the microscope from the cell surface (only that the NASA picture is less zoomed in).
Nasa image showing road illumination and in orange the India-Pakistan boarderline