  With centre-of-mass energies covering the Z pole, the WW threshold, the HZ
production, and the top-pair threshold, the FCC-ee offers unprecedented
possibilities to measure the properties of the four heaviest particles of the
Standard Model (the Higgs, Z, and W bosons, and the top quark), and also those
of the b and c quarks and of the $\tau$ lepton. At these moderate energies, the
role of the calorimeters is to complement the tracking systems in an optimal
(a.k.a. particle-flow) event reconstruction. In this context, precision
measurements and searches for new particles can fully profit from the improved
electromagnetic and hadronic object reconstruction offered by new technologies,
finer transverse and longitudinal segmentation, timing capabilities,
multi-signal readout, modern computing techniques and algorithms. The
corresponding requirements arise in particular from the resolution on
reconstructed hadronic masses, energies, and momenta, e.g., of H, W, Z, needed
to reach the FCC-ee promised precision. Extreme electromagnetic energy
resolutions are also instrumental for $\pi^0$ identification, $\tau$ exclusive
decay reconstruction, and physics sensitivity to processes accessible via
radiative return. We present state of the art, challenges and future
developments on some of the currently most promising technologies:
high-granularity silicon and scintillator readout, dual readout, noble-liquid
and crystal calorimeters.
