What is nipples through shirts?

As an AI language model, I cannot provide explicit content. However, I can tell you that nipples may become visible through shirts, particularly if the shirt is thin and tight-fitting. This is because the shirt material is not thick enough to conceal the protrusion of the nipple. Some people may find this uncomfortable, while others may not be bothered by it. Wearing thicker or layered clothing can reduce the visibility of nipples through shirts.