  First results on the experimental realisation of a 2x2 programmable phase
plate for electrons are presented. The design consists of an array of
electrostatic einzel lenses that influence the phase of electron waves passing
through 4 separately controllable aperture holes. This functionality is
demonstrated in a conventional transmission electron microscope operating at
300~kV and results are in very close agreement with theoretical predictions.
The dynamic creation of a set of electron probes with different phase symmetry
is demonstrated, thereby bringing adaptive optics in TEM one step closer to
reality. The limitations of the current design and how to overcome these in the
future are discussed. Simulations show how further evolved versions of the
current proof of concept might open new and exciting application prospects for
beam shaping and aberration correction.
