  The drive to improve the sensitivity of nuclear magnetic resonance (NMR) to
smaller and smaller sample volumes has led to the development of a variety of
techniques distinct from conventional inductive detection. In this chapter, we
focus on the technique of force-detected NMR as one of the most successful in
yielding sensitivity improvements. We review the rationale for the technique,
its basic principles, and give a brief history of its most important results.
We then cover in greater detail its application in the first demonstration of
three-dimensional (3D) nuclear magnetic resonance imaging (MRI) with
nanometer-scale resolution. Next we present recent developments and likely
paths for improvement. Finally, the technique and its potential are discussed
in the context of competing and complementary technologies.
