The development of data structures for a statistical software system is treated in this book. Data structures, e.g. storage of statistical data, handling of different kind of graphics, are very important in designing a software system. A misspecification or too narrow approach will lead to an enormous amount of reprogramming if it is possible. Chapters deal with exploratory statistical techniques, some statistical applications, exploratory projection pursuit, data structures and implementation in XploRe. Examples are given with several statistical techniques, e.g. teachware, cluster anaylsis, non-parametric regression and exploratory projection pursuit.