Open, reproducible hardware for microscopy

Reproducibility and transparency have always been central tenets of good experimental science.In recent years, these have led to 'open science' practices, including openly archived data, openly licensed code and open access to publications describing key results 1-3.However, instrumentation often lags behind data and results in terms of openness: there are, as yet, no widely adopted conventions requiring the designs of a novel instrument to be shared alongside manuscripts describing its use 4, though there is an increasing number of projects that do share plans for replication 5.This special issue collects several articles that discuss examples of projects endeavouring to adopt open hardware as a means to better reproducibility, or greater accessibility, of cutting-edge microscopy.We also include some perspectives on future directions, and on how open hardware might offer an improved way to develop and commercialize novel microscopes.This special issue is associated with a Royal Society Theo Murphy Scientific Meeting, held in Glasgow in May 2023.The meeting comprised four panel discussions with short talks from the panellists and four 'unconference' sessions that created space for discussion of a range of topics.These included technical topics, such as compatibility between projects, how to ensure users of technology are central to the development process and ways to ensure quality when designs are reproduced.We also considered challenges around