  Gene regulatory networks are powerful abstractions of biological systems.
Since the advent of high-throughput measurement technologies in biology in the
late 90s, reconstructing the structure of such networks has been a central
computational problem in systems biology. While the problem is certainly not
solved in its entirety, considerable progress has been made in the last two
decades, with mature tools now available. This chapter aims to provide an
introduction to the basic concepts underpinning network inference tools,
attempting a categorisation which highlights commonalities and relative
strengths. While the chapter is meant to be self-contained, the material
presented should provide a useful background to the later, more specialised
chapters of this book.
