The possibility of creating well controlled empty space into liquids is both, conceptually and, from the application point of view, very attractive. Since James, Cooper and co-workers coined the term porous liquid a few years ago, intense research effort has been put into this new class of materials. This review highlights most of the work published to date in this field, with special emphasis on the use of metal organic frameworks, Porous Organic Cages and Metal Organic Polyhedra as pore generators. After discussing some general considerations on the fundamentals of porous liquids, we examine the different synthetic approaches proposed to date and the main challenges in terms of materials synthesis and characterization. Finally, our view on possible future research directions is outlined.