Abstract: Disclosed are articles having authentication features, as well as methods for authenticating such articles by forming authentication features to prevent or diminish counterfeiting activities. A surface of an article to be authenticated (or a surface of a component associated with the article) may have a region with a periodic array of nanopillars comprising a polymeric material formed thereon. The array of nanopillars thus defines an authentication feature (e.g., a graphic image or other pattern). In certain aspects, the authentication feature may be substantially invisible to the human eye under normal conditions, but revealed when condensate is created on the surface by exposure to moisture or vapor (e.g., human breath). The methods of forming nanopillar arrays disclosed herein are simple and permit single-step replication with high fidelity. Furthermore, the methods may be used with a variety of substrates, including fabric, textiles, leather, glass, paper, and metals by way of non-limiting example.