  A two-dimensional Fourier transform of hadron form factors allows to
determine their charge density in transverse space. We show that this method
can be applied to any virtual photon induced transition, such as \gamma *(q)+N
-> \pi N. Only Fock states that are common to the initial and final states
contribute to the amplitudes, which are determined by the overlap of the
corresponding light-front wave functions. Their transverse extent may be
studied as a function of the final state configuration, allowing qualitatively
new insight into strong interaction dynamics. Fourier transforming the cross
section (rather than the amplitude) gives the distribution of the transverse
distance between the virtual photon interaction vertices in the scattering
amplitude and its complex conjugate. While the measurement of parton
distributions in longitudinal momentum depends on the leading twist
approximation (-q^2 -> \infty limit), all q^2<0 values contribute to the
Fourier transform, with the transverse resolution increasing with the available
range in q^2. We illustrate the method using QED amplitudes.
