  Deep inelastic electron scattering (DIS) from nucleons at low values of the
Bjorken variable $x \cong Q^2/W^2 \lsim ~ 0.1$ proceeds via fluctuations of the
photon into quark-antiquark dipole states that subsequently interact with the
gluon field in the nucleon. Dependent on the interaction energy, $W$, the
color-gauge-invariant dipole interaction with the gluon field in the nucleon,
for any fixed dipole size, contains the limits of i) color transparency and ii)
saturation, where "saturation" stands for the approach to a hadronlike
dipole-proton interaction cross section. All essential features of the
experimental results on low-x DIS, as a consequence of the
color-gauge-invariant dipole interaction follow model independently i.e.
without specific ansatz for the dipole cross section. The model-independent
results in particular include the low-x scaling behavior of the photoabsorption
cross section, $\sigma_{\gamma^*p} (W^2,Q^2) = \sigma_{\gamma^*p} (\eta
(W^2,Q^2))$, with definite functional dependence on the low-x scaling variable
$\eta (W^2,Q^2) \cong Q^2/\Lambda^2_{sat} (W^2)$ in the limits of $\eta
(W^2,Q^2) \gg 1$ and $\eta (W^2,Q^2) \ll 1$, respectively. Consistency with the
pQCD-improved parton model implies the definite value of $C_2 \cong 0.29$ for
the exponent in the "saturation scale", $\Lambda^2_{sat} (W^2) \approx
(W^2)^{C_2}$. The longitudinal-to-transverse ratio of the photoabsorption cross
section at large $Q^2$ has the definite value of $R = 1/2 \rho$ with $\rho =
4/3$. For $W^2 \to \infty$ at any fixed $Q^2$, the photoabsorption cross
section converges towards a $Q^2$-independent saturation limit that coincides
with the cross section for $Q^2 = 0$ photoproduction.
