  We describe how known matter effects within a well-motivated particle physics
framework can explain the dark energy component of the Universe. By considering
a cold gas of particles which interact via a vector mediator, we show that
there exists a regime where the gas reproduces the dynamics of dark energy. In
this regime the screening mass of the mediator is proportional to the number
density of the gas, hence we refer to this phenomenon as "the adaptive
screening mechanism". As an example, we argue that such screening mass can
result from strong localization of the vector mediators. The proposed dark
energy mechanism could be experimentally verified through cosmological
observations by the Euclid experiment, as well as by studying properties of
dark photons and sterile neutrinos.
