  This article has been published as a chapter in "Chemical Reactivity Theory:
A Density Functional View", ed. P. K. Chattaraj (CRC Press, New York, 2009),
ch. 8, p. 105. In it, an overview of the relationship between time-dependent
DFT and quantum hydrodynamics is presented, showing the role that Bohmian
mechanics can play within the ab-initio methodology as both a numerical and an
interpretative tool.
