  Understanding the human brain remains one of the most significant challenges
of the 21st century. As theoretical studies continue to improve the description
of the complex mechanisms that regulate biological processes, in parallel
numerous experiments are conducted to enrich or verify these theoretical
predictions and with the aim of extrapolating more accurate models. In the
field of magnetometers for biological application, among the various sensors
proposed for this purpose, NV centers have emerged as a promising solution due
to their perfect biocompatibility and the possibility of being positioned in
close proximity and even inside the cell, allowing a nanometric spatial
resolution. There are still many difficulties that must be overcome in order to
obtain both spatial resolution and sensitivity capable of revealing the very
weak biological electromagnetic fields generated by neurons (or other cells).
However, over the last few years, significant improvements have been achieved
in this direction, thanks to the use of innovative techniques, which allow us
to hope for an early application of these sensors for the measurement of fields
such as the one generated by cardiac tissue, if not, in perspective, for the
nerve fibers fields. In this review, we will analyze the new results regarding
the application of NV centers and we will discuss the main challenges that
currently prevent these quantum sensors from reaching their full potential.
