As the energy consumed by datacentres grows, finding energy-efficient alternatives to conventional electronics becomes increasingly urgent. Molecular electronics offers a different idea of what a device can be: using synthetic chemistry, custom molecules can be designed for specific applications, utilising fascinating nanoscale phenomena such as quantum interference. These single-molecule devices can “self-assemble” into larger structures for energy-efficient sensing, memory, and computation. The nanostructured nature of single molecules offers endless possibilities, and difficulties: wiring molecules into circuits requires sub-nanometer (< 0.000000001 m!!!) precision. The scanning tunnelling microscope (STM), which explores surfaces at the atomic scale using quantum tunnelling, could become the multimeter of molecular electronics, but commercial STMs are extremely expensive and not optimised for these experiments. This talk describes the development of an open-hardware STM for single-molecule “break-junction” experiments (SMolSTM). The design was developed over several years, from a prototype built in a shed during the COVID-19 pandemic to a precision instrument currently in use in a state-of-the-art low noise research facility. This STM is orders of magnitude less expensive than commercial alternatives and can be made using hand tools and 3D printing, yet achieves exceptional performance in single-molecule experiments. The flexibility of open hardware allows experiments which are impossible on existing systems. This talk will introduce molecular electronics, outline a multi-year journey in DIY STM development, and describe some experiments using SMolSTM (e.g. measuring the resistance of a single gold atom!). This work was conducted in part at Lancaster University as part of an EPSRC funded research project.