Atomic-scale measurements with custom-built scanning tunneling microscopes in specialized environments

Scanning tunneling microscopy (STM) has become a cornerstone of atomic-scale research, as modern experiments demand not only high spatial resolution but also flexible instrumentation capable of supporting electrical and optical measurements. Custom-built STMs provide distinct advantages in specialized environments, including cryogen-free superconducting magnets, water-cooled magnet systems, millikelvin cryostats, and platforms integrating optical or terahertz excitation. These systems enable experiment-specific optimization of mechanical design, vibration isolation, thermal coupling, and low-noise signal pathways, routinely achieving sub-picometer stability and supporting advanced measurement modalities. Recent advances, including terahertz-driven STM, electron spin resonance combined STM, and spectroscopic measurements under extreme conditions, highlight the unique scientific opportunities enabled by custom-designed STM platforms. This review outlines the engineering principles underpinning high-performance custom-built STMs and highlights key discoveries enabled by their versatility. We further address ongoing challenges, including drift suppression, electromagnetic interference, and reliable tip preparation. Finally, emerging directions toward next-generation STM platforms promise enhanced stability, ultrafast temporal resolution, and expanded access to atomic-scale quantum phenomena.