Chemistry deals with complex molecular systems that can be further connected by supramolecular interactions and reaction networks. However, chemists have taken little advantage of the intrinsic complexity of chemical systems, probably due to the lack of appropriate tools to analyse and understand complexity. In the last few decades, the concept of complexity has grown appealing: it allows the design of networks and dynamic systems expressing emerging properties and functions, which would be difficult to achieve from the mere addition of the components of the ensemble. Here we describe a personal overview of the recent state-of-the-art in the field, mainly focused on complex systems providing molecular recognition and catalysis. Far from being a thorough revision of the recent literature, we intend to illustrate the topic to attract the chemical community for considering complexity as an additional parameter in their research.