Metrics and User Engagement researchers at Yahoo Research collaborate with our Search and Personalization teams to study and define metrics for experimentation, user engagement, and product success. Statistical analysis and data-driven user understanding methods are employed to enable the optimization of products through rigorous experimentation, in addition to generative and exporatory statistical analysis. Researchers help to guide product development by unlocking large-scale data to provide deep, grounded analysis. We also aid Yahoo as a whole in driving data integrity and clean data practices. Our passion is a user-centric approach to Big Data, ensuring long-term happy and engaged users.