  Backscatter Communication (BackCom), which is based on passive reflection and
modulation of an incident radio-frequency (RF) wave, has emerged as a
cutting-edge technological paradigm for self-sustainable Internet-of-things
(IoT). Nevertheless, the contemporary BackCom systems are limited to
short-range and low data rate applications only, thus rendering them
insufficient on their own to support pervasive connectivity among the massive
number of IoT devices. Meanwhile, wireless networks are rapidly evolving
towards the smart radio paradigm. In this regard, reconfigurable intelligent
surfaces (RISs) have come to the forefront to transform the wireless
propagation environment into a fully controllable and customizable space in a
cost-effective and energy-efficient manner. Targeting the sixth-generation (6G)
horizon, we anticipate the integration of RISs into BackCom systems as a new
frontier for enabling 6G IoT networks. In this article, for the first time in
the open literature, we provide a tutorial overview of RIS-assisted BackCom
(RIS-BackCom) systems. Specifically, we introduce the four different variants
of RIS-BackCom and identify the potential improvements that can be achieved by
incorporating RISs into BackCom systems. In addition, owing to the unrivaled
effectiveness of non-orthogonal multiple access (NOMA), we present a case study
on an RIS-assisted NOMA-enhanced BackCom system. Finally, we outline the way
forward for translating this disruptive concept into real-world applications.
