The possibility of creating well-controlled empty space within liquids is conceptually intriguing, and from an application perspective, full of potential. Since the concept of porous liquids (PLs) arose several years ago, research efforts in this field have intensified. This review highlights the design, synthesis, and applicability of PLs through a thorough examination of the current state-of-the-art. Following a detailed examination of the fundamentals of PLs, we examine the different synthetic approaches proposed to date, discuss the nature of PLs, and their pathway from the laboratory to practical application. Finally, possible challenges and opportunities are outlined.