At Nature Physics we enjoy putting together the occasional Insight consisting of a number of authoritative Reviews covering an important topic in physics. This month, we've joined forces with Nature Materials to produce an Insight on quantum materials (http://go.nature.com/2hNXJHa) — an emerging theme that we've already picked up on in the recent past (Nat. Phys. 12, 105; 2016).

We are particularly pleased to acknowledge our sponsors, the Gordon and Betty Moore Foundation and the Simons Foundation. Thanks to their support, we are able to offer free online access of the Insight for six months, in addition to distributing print copies at the upcoming Materials Research Society fall meeting in Boston and the American Physical Society March meeting in Los Angeles.

Finding a definition for quantum materials that is unanimously agreed on is tricky, but it seems like a growing number of scientists working at the frontiers of physics and materials science know a quantum material when they see one. This Insight attempts to define the field in more detail by examining the physics of quantum materials, their synthesis and design, the control over their properties, and the functionality they give rise to.

Of course we cannot hope to provide a fully comprehensive overview of the entire field in a single supplement, but we do hope it will prove an inspiring reflection of the field. Enjoy.