  The evolution toward sixth-generation (6G) wireless networks has introduced
programmable wireless environments (PWEs) and reconfigurable intelligent
surfaces (RISs) as transformative elements for achieving near-deterministic
wireless communications. However, the enhanced capabilities of RISs within
PWEs, especially as we move toward more complex electromagnetic functions by
increasing the number of reflecting elements, underscore the need for
high-precision user localization, since inaccurate localization could lead to
erroneous configuration of RISs, which would then compromise the effectiveness
of PWEs. In this direction, this paper investigates the integration of RISs and
optical anchors within PWEs, emphasizing the crucial role of ultra-precise
localization in unlocking advanced electromagnetic functionalities.
Specifically, we present an in-depth analysis of various localization
techniques, both RISbased and RIS-independent, while introducing the concept of
empowering PWEs with optical anchors for enhanced localization precision. Our
findings highlight that accurate localization is essential to fully exploit the
capabilities of RISs, paving the way for future applications. Through this
exploration, we contribute to the advancement of PWEs in line with the
ambitious goals of the 6G standards and improve the quality of service in next
generation wireless networks.
