Nanotech

The technical definition of nanotechnology is any technology which functions on a scale best measured in nanometers, but especially that which deals with the manipulation of individual molecules or atoms.
In practice, however, "nanotech" is colloquially used to refer to any technology that is smaller than the naked eye can see.  Most of what is referred to as "nanotech" is actually microtechnology, i.e. technology which functions on a scale best measured in micrometers; the microscopic scale.  There is some true nano-level technology out there, but most of it is in static nanomaterials with odd properties.
The majority of nanotech is microscopic, programmable machines called nanobots, which tend to be used in swarms or colonies that self-replicate to maintain their numbers.  These can be made to accomplish a variety of tasks related to cybernetics or biologics, as well as applications in medicine, materials, construction, science, space exploration and basically every other field.
Due to its size, no nanotech has yet been made that can respond to any type of wireless signal.  It cannot be controlled or re-programmed wirelessly, and it is immune to EMP blasts for the same reason.  Microwaves, however, can affect nanotech, often in unpredictable ways.