Most people don't think about how molecules fit in the ultra-small spaces between other molecules, but that is what Professor Masahide Takahashi's research team think about every day at Osaka Metropolitan University. They study metal-organic frameworks (MOFs), composed of modularly arranged metal ions and molecules (organic linkers), forming a scaffold. Metal ions act as corners connected by longer organic linkers. A MOF can be made using different metals and organic linkers, so they can be designed for specific chemical/physical properties, attractive for coating sensors in optical and electronic devices. This is because the MOF scaffold leaves a lot of internal space open. These pores can host numerous guest molecules that can access the MOFs' huge internal surface area, which make them ideal for developing catalytic materials, gas storage, gas separation, and environmental remediation.