The atomic force microscope is widely used to image surfaces with atomic and molecular resolution, in both vacuum and liquid. At the heart of this instrument is a nanomechanical device—a cantilever whose length is the thickness of a human hair—which can transduce external stimuli, such as a pico-Newton-scale force, into a measurable signal. In this talk, I will give an overview of the diverse capabilities of these simple nanomechanical devices by discussing recent work in my group on two applications. First, I will discuss how to measure the force between two atoms in vacuum and our recent discovery that certain force laws can evade measurement. Second, I will present a protocol to measure the hydrodynamic boundary condition on individual nanoparticles, and an experimental exploration of the Navier slip condition. The reported experiments are performed by collaborators at the Argonne National Laboratory, Massachusetts Institute of Technology, University of Maryland Baltimore County and the University of Regensburg.