Simply enter the question "are eggs dairy?" in your favorite search engine to experience how classification can shape our view of the world. The search results will include all kinds of articles, discussions, and even videos from people asking and trying to answer this question—generally because eggs are placed in the dairy section of most US grocery stores.
This implicit classification leads many people in the US to believe that eggs are dairy. This may be a surprising assumption to those in other countries such as the UK where eggs are kept in the dry goods section. We often are not aware of the way classification shapes our perceptions and decisions. Classification of eggs in the grocery store is, for most of us, a low-stakes problem. Classification of pharmaceutical products, on the other hand, can have massive clinical and economic effects, but for most individuals, the classification is just as invisible.