  We demonstrate the creation of a charge density wave (CDW) along a stack of
coupled Josephson junctions in layered superconductors. Electric charge in each
superconducting layer oscillates around some average value, forming a breathing
CDW. We show the transformation of a longitudinal plasma wave to CDW in the
state corresponding to the outermost branch. Transitions between different
types of CDW's related to the inner branches of current voltage characteristics
are demonstrated. The effect of the external electromagnetic irradiation on the
states corresponding to the inner branches differs crucially from the case of
the single Josephson junction. The Shapiro steps in the IV-characteristics of
the junctions in the stack do not correspond directly to the frequency of
radiation $\omega$. The system of Josephson junctions behaves like a single
whole system: the Shapiro steps or their harmonics in the total
IV-characteristics appear at voltage $\sum V_l=N_R\frac{m}{n}\omega$, where
$V_l$ is the voltage in $l$-th junction, $N_R$ is the number of JJ in the
rotating state, and $m$ and $n$ are integer numbers.
