  A Martian meteorite, magnetic inks, drug targeting, batteries, contrasts for
MRI, data storage or even clinical thermo-therapy seem to have no connection,
but all have in common a dark mineral called magnetite. However, in each of
these applications this iron oxide shows up with different forms because their
optical, electrical and magnetic properties are strongly dependent on size,
shape and kind of surfactant. In this sense the control of this characteristics
has long been of scientific and technological interest. In an AC magnetic
field-assisted cancer therapy, \textit{e.g.}, from a biological point of view,
the interaction of the nanoparticles with cells is critically determined by the
surface properties which control their fate in biological environments. Besides
the size, factors as the shape also seems to affect the cellular uptake. On the
other hand, the specific absorption rate (SAR) at a fixed frequency and
magnetic field, is hugely dependent on average and distribution of size, shape,
crystalline anisotropy, and degree of aggregation or agglomeration of the
nanoparticles. Each of these factors contributes to an independent energy loss
mechanism: N\'eel relaxation, Brown relaxation or magnetic hysteresis loss.
Thus, the key for improving the efficiency of a given application is the
knowledge about the morphological control.
