When designing search user interfaces (SUIs), there is a need to target specific user groups. The cognitive abilities, fine motor skills, emotional maturity and knowledge of a sixty years old man, a fourteen years old teenager and a seven years old child differ strongly. These abilities influence the decisions made in the user interface (UI) design process of SUIs. Therefore, SUIs are usually designed and optimized for a certain user group. However, especially for young and elderly users, the

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... sign requirements change rapidly due to fast changes in users' abilities, so that a flexible modification of the SUI is needed. In this positional paper we introduce the concept of an evolving search user interface (ESUI). It adapts the UI dynamically based on the derived capabilities of the user interacting with it. We elaborate on user characteristics that change over time and discuss how each of them can influence the SUI design using an example of a girl growing from six to fourteen. We discuss the ways to detect current user characteristics. We also support our idea of an ESUI with a user study and present its first results.