Do-It-Yourself (DIY) systems offer cost-effective and customizable solutions for researchers who require specialized equipment that is not readily available or affordable commercially. In fact, there are a number of systems for home cage monitoring (HCM) behavior that have been built independently. This concept is supported by new trends in the development of software and electronic hardware. By combining off-the-shelf hardware with open-source software, DIY systems enable the creation of prototypes that can be scaled into robust, mature systems for long-term experiments. The chapter explores the advantages and challenges of DIY systems compared to commercial solutions, emphasizing the importance of detailed documentation, modular design, and adherence to animal welfare standards. Key considerations include system design, housing conditions, enrichment tools, activity tracking, individual vs. group tracking, synchronization, and data processing. Strategies for minimizing single points of failure (SPOFs) and ensuring reliable power and data infrastructure are discussed. The chapter also highlights the significance of sharing DIY systems and data in open-source repositories to promote transparency, reproducibility, and collaboration within the scientific community. By following best practices, researchers can develop effective and scalable DIY HCM systems that enhance the quality and reproducibility of animal research while reducing costs.