  The scanning transmission electron microscope, a workhorse instrument in
materials characterization, is being transformed into an atomic-scale material
manipulation platform. With an eye on the trajectory of recent developments and
the obstacles toward progress in this field, we provide a vision for a path
toward an expanded set of capabilities and applications. We reconceptualize the
microscope as an instrument for fabrication and synthesis with the capability
to image and characterize atomic-scale structural formation as it occurs.
Further development and refinement of this approach may have substantial impact
on research in microelectronics, quantum information science, and catalysis
where precise control over atomic scale structure and chemistry of a few
"active sites" can have a dramatic impact on larger scale functionality and
where developing a better understanding of atomic scale processes can help
point the way to larger scale synthesis approaches.
