New tool for surface modification: The 2D pattern formed by physisorbed dehydrobenzoannulene molecules on a graphite surface depends on their concentration in solution. The concentration dependence is directly related to the difference in stability between the linear and the honeycomb polymorphs and their respective molecular densities (see picture). Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2002/2008/z705322_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

One Building Block, Two Different Supramolecular Surface‐Confined Patterns: Concentration in Control at the Solid–Liquid Interface