Data structures are the science of organizing and accessing data, and their study is a core part of computer science. They underpin our computing infrastructure with efficiency being of critical importance. As the computing landscape changes with more demanding tasks arising, data structure research remains vibrant, with two aspects coming particularly in focus: scalability and adaptivity. Scalability means that data structures remain efficient as data sets increase, become more dynamic, and become more distributed. Adaptivity implies taking advantage of modern hardware, such as multicore computation or memory hierarchies, as well specific structure and biases in the operations performed. One seeks to create structures that maximally take advantage of such architectural and distributional details without any foreknowledge of them. General limits of adaptivity have long posed deep theoretical questions, which continue to inspire research. This Dagstuhl Seminar is part of a successful series begun in 1991. The series has contributed to shaping trends in data structures research.