This article attempts to present a modern viewpoint of solids from an elementary and yet fundamental point of view. The unifying concept used is that of the “particles” of solid-state physics. Electrons (with spin), holes, phonons, plasmons, and magnons are discussed. The interaction of these particles is discussed in experiments involving light absorption, x rays, magnetic resonance, the Mössbauer effect, neutron scattering, electron beams, charge and heat transport, and acoustic absorption.