It has been realized in recent years that the low energy frontier is a 
rich complement to the conventional high energy particle physics 
landscape. As a consequence, the once few active experiments have 
grown into a wide panorama with an interesting potential for future 
development. Phenomena such as photon-photon scattering, as predicted 
by QED, and sub-eV particle production (Axion-Like Particles, Mini-
Charged Particles, chameleons, to mention a few) are investigated 
using low energy (1-2 eV) photons as probes of a target vacuum region 
where electromagnetic energy is present, a magnetic field for 
instance. The properties of the emerging photon beam, typically its 
intensity and polarization, carry information on the physical 
processes which took place, much in the same fashion as scattering 
experiments at particle accelerators. The coupling of Axion-Like-
Particles to to photons is also exploited by observatory type 
experiments, where the signature of ALPs from astrophysical sources or 
of cosmological origin is sought in the form of photons produced by 
the interaction of these particles with a magnetic field.
The current panorama of experimental efforts probing many aspect of 
this Low Energy Frontier will be reviewed, with an emphasis on the 
variety of techniques employed and on the potential for a major 
discovery.