  The intelligent reflecting surface (IRS) alters the behavior of wireless
media and, consequently, has potential to improve the performance and
reliability of wireless systems such as communications and radar remote
sensing. Recently, integrated sensing and communications (ISAC) has been widely
studied as a means to efficiently utilize spectrum and thereby save cost and
power. This article investigates the role of IRS in the future ISAC paradigms.
While there is a rich heritage of recent research into IRS-assisted
communications, the IRS-assisted radars and ISAC remain relatively unexamined.
We discuss the putative advantages of IRS deployment, such as coverage
extension, interference suppression, and enhanced parameter estimation, for
both communications and radar. We introduce possible IRS-assisted ISAC
scenarios with common and dedicated surfaces. The article provides an overview
of related signal processing techniques and the design challenges, such as
wireless channel acquisition, waveform design, and security.
