The aim of this chapter is to present and discuss the theoretical framework “Personalized Mathematics and Mathematics Inquiry” (PMMI) which supported the design and development of the Cyprus Mathematics Textbooks. The PMMI framework involves a set of Personalized Mathematics practices in which students actively set mathematics goals, engage, reason, discuss, create, make connections, solve problems, and reflect on mathematical content. Mathematics instruction, within this framework, seeks to actively involve students in authentic and personally relevant learning experiences. Mathematics Inquiry is at the core of the PMMI framework and evolves in three learning phases, “romance,” “precision,” and “generalization.” Mathematics Inquiry consists of challenging problems, namely explorations and investigations, which capture students’ curiosity and invite them to make hypotheses and pursue their hunches. The goal of an exploration, at the beginning of each chapter, is to elicit motivation, which will ignite students’ personal inquiry. Inevitably, students bring their own experiences in these explorations, and thus, differentiation and personal learning are facilitated. Each exploration is followed by an investigation. Investigations, however, are more closed and guided than explorations. To respond to these investigations, students often need to analyze, form hypotheses, and work systematically with various strategies, using different mathematical tools, manipulatives, and applets. During these investigations, the teachers’ role is to facilitate students to control their own learning. At this stage, new mathematical concepts and vocabulary are introduced. The application of the PMMI framework is exemplified through examples taken from the mathematics textbooks.