Graph databases have gained increasing popularity recently, disrupting areas traditionally dominated by conventional relational, SQL-based databases, as well as domains requiring the extra capabilities afforded by graphs. This book is a timely effort to capture the state of the art of Graph databases and their applications in domains, such as Social Media analysis and Smart Cities.This practical book aims at combining various advanced tools, technologies, and techniques to aid understanding and better utilizing the power of Social Media Analytics, Data Mining, and Graph Databases. The book strives to support students, researchers, developers, and simple users involved with Data Science and Graph Databases to master the notions, concepts, techniques, and tools necessary to extract data from social media or smart cities that facilitate information acquisition, management, and prediction.The contents of the book guide the interested reader into a tour starting with a detailed comparison of relational SQL Databases with NoSQL and Graph Databases, reviewing their popularity, with a focus on Neo4j.