Hybrid power plants (HPPs) combining multiple generation and/or storage sources behind a single connection point are becoming popular due to their capability to provide additional value for both plant owners and power systems compared to individual technology renewable power plants. However, the research on HPPs is still in nascent stage. This article comprehensively overviews utility-scale HPPs (power plants ranging from hundreds of MW to GW scale). It primarily addresses HPPs that combine renewable sources such as wind and solar (PV technology) with electrical energy storage (ESS), all connected behind a single grid connection and operated as a unified power plant by a single operator. This article covers various aspects such as HPPs' potential benefits, research challenges, and opportunities related to their design, operation, and development, from both societal and HPP owners' perspectives. It briefly discusses the advantages of HPPs compared to individual renewable technology-based power plants highlighting the potential added values of HPPs for owners, system operators, and society, while ensuring compliance with grid code requirements at the point of common coupling. The main focus is on identifying and clustering the research challenges associated with design and operation of HPPs. Topics such as energy management systems, sizing and siting, electrical design and control, uncertainties and forecasting, grid emulation and advanced testing, and multi-energy system integration are elaborated and reviewed. This article demonstrates that significant research is urgently needed to enhance renewable generation flexibility and improve grid services. Addressing these challenges will accelerate the development and deployment of HPPs.