In summary, it was found that: (i) all the aforementioned enhanced-separation technologies have high potentials for enhanced hydro- cyclone separation. (ii) To date, there are no effective ways of mod- ifying operations to overcome some inherent problems associated with hydrocyclones, especially particle misplacements. (iii) It is urgently necessary to apply hydrocyclones to realize the better separation of materials with complex or extreme parameters, including shape, size, density, and concentration, from liquid with low energy consumption and small split ratio. For example, the separation of the fibers, sub- micron particles, materials with density closed to the liquid density, and the ultra-low concentration solid-liquid mixture. (iv) As a result, hydrocyclones can be successfully employed in more industries, espe- cially the disposal of solid waste, wastewater, and waste gas in petro- chemical, HVAC (heating, ventilation, and air conditioning), nuclear, aviation, aerospace, and other heavy industries. Additionally, (v) there is a serious need for the development and utilization of universal en- hanced-separation hydrocyclone technologies, hydrocyclone models, software packages covering a number of universal hydrocyclone models, which can be extensively and conveniently applied in almost all application fields for optimizing hydrocyclone design and operation, and hydrocyclones with artificial intelligence.