  Despite their success, General Relativity (GR) and the Standard Model (SM)
are currently understood as effective field theories only valid up to some
energy (length) scale, where new physics is expected to appear. We review the
framework of extended relativity (ER) in Clifford spaces (C-spaces),
summarising some of its concepts, methods and results. We also discuss likely
links of this approach with other relativies (OR), beyond GR and SM theories,
recent ideas from emergent spacetime (ES) and quantum entanglement (QE), in
search for quantum gravity (QG) and unification (U). Finally, we explore and
expose the need to go even beyond ER, and the challenges it poses, from both
experimental and theoretical sides.
