  The lensing of CMB photons by intervening large-scale structure leaves a
characteristic imprint on its arcminute-scale anisotropy that can be used to
map the dark matter distribution in projection on degree scales or ~100 Mpc/h
comoving. We introduce a new algorithm for mass reconstruction which optimally
utilizes information from the weak lensing of CMB anisotropies in the damping
tail. It can ultimately map individual degree scale mass structures with high
signal-to-noise. To achieve this limit an experiment must produce a high
signal-to-noise, foreground-free CMB map of arcminute scale resolution,
specifically with a FWHM beam of < 5' and a noise level of < 15 (10^-6-arcmin)
or 41 (uK-arcmin).
