Femtotechnology / Femtotech
Image from Bernd Helfert
There are technologies that produce effects on the femtoscale, but 'femtotech' is a particular term, analogous to 'nanotech'. Users of the word imagine a technology or set of technologies that rearranges matter on the femtoscale, with something analogous to nanotechnology's scope and precision. Femtotech would supposedly allow precision arrangement of the elementary particles that make up atoms. This would supposedly allow such things as transmutation of elements without the use of massive facilities or the release of radiation, the creation of various kinds of exotic stable or metastable elements and other fantastic effects.
Real 'femtotech' effects and materials are extraordinarily limited in scope, despite important niche uses. Despite this, the term persists. One usage is as a synonym for clarketech, since femtotech would presumably produce some similarly magical effects. 'Femtotech' is also sometimes used in works of fantasy or science fiction, or features in popular superstition and rumours, but it is not experienced in this universe outside of some virch worlds.
See also FTL, time travel, picotech.