  In the Internet of Things era, an increasing number of household devices and
everyday objects are able to send to and retrieve information from the
Internet, offering innovative services to the user. However, most of these
devices provide only smartphone or web interfaces to control the IoT object
properties and functions. As a result, generally, the interaction is
disconnected from the physical world, decreasing the user experience and
increasing the risk of isolating the user in digital bubbles. We argue that
tangible interaction can counteract this trend and this paper discusses the
potential benefits and the still open challenges of tangible interaction
applied to the Internet of Things. To underline this need, we introduce the
term Internet of Tangible Things. In the article, after an analysis of current
open challenges for Human-Computer Interaction in IoT, we summarize current
trends in tangible interaction and extrapolate eight tangible interaction
properties that could be exploited for designing novel interactions with IoT
objects. Through a systematic literature review of tangible interaction applied
to IoT, we show what has been already explored in the systems that pioneered
the field and the future explorations that still have to be conducted.
