  This colloquium addresses the issue of the shape of hadrons and in particular
that of the proton. The concept of shape in the microcosm is critically
examined. Special attention is devoted to properly define the meaning of shape
for bound-state systems of near massless quarks. The ideas that lead to the
expectation of non-sphericity in the shape of hadrons, the calculations that
predict it, and the experimental information obtained from recent
high-precision measurements are examined. Particular emphasis is given to the
study of the electromagnetic transition between the nucleon and its first
excited state, the $\Delta$(1232)-resonance. The experimental evidence is is
critically examined and compared with lattice calculations, as well as with
effective-field theories and phenomenological models.
