  High intense electromagnetic fields can be unique probes to study natures of
macroscopic vacua by themselves. Combining accelerators with the intense field
can provide more fruitful probes which can neither be achieved by only intense
fields nor only high energy accelerators. We will overview the natures of vacua
which can be accessible via intense laser-laser and intense laser-electron
interactions. In the case of the laser-laser interaction, we propose how to
observe nonlinear QED effects and effects of new fields like light scalar and
pseudo scalar fields which may contribute to a macroscopic nature of our
universe such as dark energy. In the case of the laser-electron interaction, in
addition to nonlinear QED effects, we can further discuss the nature of
accelerating field in the vacuum where we can access physics related with event
horizons such as Hawking-Unruh radiations. We will introduce a recent
experimental trial to search for this kind of odd radiations.
