  The focused ion beam (FIB) is a powerful tool for the fabrication,
modification and characterization of materials down to the nanoscale. Starting
with the gallium FIB, which was originally intended for photomask repair in the
semiconductor industry, there are now many different types of FIB that are
commercially available. These instruments use a range of ion species and are
applied broadly in materials science, physics, chemistry, biology, medicine,
and even archaeology. The goal of this roadmap is to provide an overview of FIB
instrumentation, theory, techniques and applications. By viewing FIB
developments through the lens of the various research communities, we aim to
identify future pathways for ion source and instrumentation development as well
as emerging applications, and the scope for improved understanding of the
complex interplay of ion-solid interactions. We intend to provide a guide for
all scientists in the field that identifies common research interests and will
support future fruitful interactions connecting tool development, experiment
and theory. While a comprehensive overview of the field is sought, it is not
possible to cover all research related to FIB technologies in detail. We give
examples of specific projects within the broader context, referencing original
works and previous review articles throughout.
