This book covers topics on engineering science, technology and applications of the classification of particles in liquids suspensions in hydrocyclones. It is divided into 12 chapters starting with the introduction of the hydrocyclone to the mining industry and its several applications of classification, followed by the fundamentals of classification. A special chapter on the fundamentals of sedimentation as the mechanism of the hydrocyclone classification is given. The authors also cover the fundamentals hydrodynamics of solid-fluid interaction with application to the fluids and suspensions flow of in circular pipelines and discusses the flow pattern in hydrocyclones from a fluid dynamics point of view. The physical design, the empirical, phenomenological and numerical hydrocyclone models are presented. The two last chapters deal with the applications of hydrocyclones system design and instrumentation study cases of application in hydrocyclones to the mining industry. Several parts of this book are the result of the work of their research and professional groups from the university and industry.