This handbook is part of the MonksHillLab initiative (Working group for Ecophysiology and Water and Matter Cycling (ECO) of the Leibniz Centre for Agricultural Landscape Research (ZALF)), which aims to democratize science by enabling low-cost, DIY sensor development for environmental monitoring. It provides step-by-step guidance on building and calibrating sensor systems using open hardware and widely available components. The project supports ecophysiological research and the discovery of sustainable agricultural management practices, particularly in under-resourced regions and the Global South. By focusing on reproducibility, accessibility, and practical application, it seeks to close the gap between research/development and field implementation/adoption. This is a living document: users are encouraged to build upon the existing designs, share adaptations, and contribute new chapters. You’re very welcome to share your improvements/chapters. Just email the author (mathias.hoffmann@zalf.de) and submit an update. Future versions will include additional low-cost DIY systems and their integration with the MonksHillLab Logger App. Thus, together, we aim to grow with that handbook a practical, evolving resource for scientists, students, and practitioners. We are currently exploring the idea of organizing a low-cost sensor summer school and/or online workshop to provide hands-on training, exchange ideas, and build a global community around DIY environmental monitoring. If you are interested in participating or helping shape the format, feel free to get in touch or respond to the feedback link: https://docs.google.com/forms/d/e/1FAIpQLSd-lZMnjAK-ll1-eMoKwWdKpjrdHeFioPDRd5Fp-lMQW38EWg/viewform?usp=header Whats New? Version 2.2 introduces the "lab on Wheels" Maker Space, a fully power autark (solar powered) programming and construction facility. No lab? No tools? No problem! in addition, author are now listet per chapter. Whats Next? Version 2.3 will add a new chapter presenting a low cost system for flush-sampling of chamber headspace air for lateron analyses at a GCMS, as well as the introduction of a new regional hub located in Germany.