  The Particle Flow Algorithms adopted for future $e^{+}e^{-}$ colliders
detectors and phase-II CMS upgrade require very high granularity calorimeters
to deconvolve the individual contributions of particles in jets. This is
especially true for electromagnetic calorimeters (ECAL). For a realistic large
detector many technological requirements have to be fulfilled: modularity for
industrialization; compact integration of an embedded very front-end
electronics featuring large dynamics, low-power and self-triggering; mechanical
structure and cooling systems with minimal dead zones. The technological
prototype of the silicon-tungsten (SiW) ECAL presented here should achieve all
this. 10 layers are produced and tested in beam, while design and optimization
studies are ongoing on a variety of simulated key processes to test the
performance of the hardware and the algorithms.
