  In this article, we overview intelligent reflecting surface (IRS)-empowered
wireless communication systems. We first present the fundamentals of
IRS-assisted wireless transmission. On this basis, we explore the integration
of IRS with various advanced transmission technologies, such as millimeter
wave, non-orthogonal multiple access, and physical layer security. Following
this, we discuss the effects of hardware impairments and imperfect
channel-state-information on the IRS system performance. Finally, we highlight
several open issues to be addressed.
