  In this paper we clarify the nature of $\pi$ and $\pi+\sigma$ electron
excitations in pristine graphene. We clearly demonstrate the continuous
transition from single particle to collective character of such excitations and
how screening modifies their dispersion relations. We prove that $\pi$ and
$\pi+\sigma$ plasmons do exist in graphene, though occurring only for a
particular range of wavevectors and with finite damping rate. The particular
attention is paid to compare the theoretical results with available EELS
measurements in optical ($\mathrm{Q\approx 0}$) and other ($\mathrm{Q\neq 0}$)
limits. The conclusions, based on microscopic numerical results, are confirmed
in an approximate analytical approach.
