The 200 nanometre insulating layer on the insulating single glazing is so thin that the human eye can look through it. A nanometre is one billionth of a meter, or 0.000 000 001 m. By way of comparison: a human hair is approximately 80,000 nanometres thick. 200 nanometres therefore is very, very thin and thus practically invisible. But in a number of situations, under certain lighting conditions, you can see the very thin layer as a more or less diffuse effect.
Under a strong incidence of sunlight, the insulating nano layer can be seen, as in the photo, by the dark green of the trees.