A microscope that can see atoms
Let’s freeze carbon monoxide to -266° centigrade* to make a needle with a single molecule on its end. Then we’ll use that needle to make a crazy super-precise scanning-tunnelling microscope that can “determine the location of atoms within molecules.”
Why? First of all, why not? Secondly, it can allow the creation of ultra-pure materials, like building a brick wall with every brick and every space perfectly sized.