No other concepts have shaken so deeply the bases of engineering like those of positive
and negative feedback. They have played a most prominent role in engineering since the beginning
of the previous century. The birth certificate of positive feedback can be traced back to a pair of
patents by Edwin H. Armstrong in 1914 and 1922, whereas that of negative feedback is already
lost in time. We present in this paper a short review on the feedback's origins in the fields of
engineering and biology. Besides, we compare the main feedback's ideas in control theory and
system biology in order to get a better understanding of the lactose and tryptophan operons' regulatory
systems (control systems). It is obvious that we need to know the genome of an organism
in order to understand how it works, but that is only half of the puzzle, for we also need to know
how the underlying genetic regulatory systems work in order to get a complete picture of the cell's
dynamics.