  The atmospheres filling massive galaxies, groups, and clusters display
remarkable similarities with rainfalls. Such plasma halos are shaped by AGN
heating and subsonic turbulence (~150 km/s), as probed by Hitomi. The new 3D
high-resolution simulations show the soft X-ray (< 1 keV) plasma cools rapidly
via radiative emission at the high-density interface of the turbulent eddies,
stimulating a top-down condensation cascade of warm, $10^4$ K filaments. The
ionized (optical/UV) filaments extend up to several kpc and form a skin
enveloping the neutral filaments (optical/IR/21-cm). The peaks of the warm
filaments further condense into cold molecular clouds (<50 K; radio) with total
mass up to several $10^7$ M$_\odot$, i.e., 5/50$\times$ the neutral/ionized
masses. The multiphase structures inherit the chaotic kinematics and are
dynamically supported. In the inner 500 pc, the clouds collide in inelastic
way, mixing angular momentum and leading to chaotic cold accretion (CCA). The
BHAR can be modeled via quasi-spherical viscous accretion with collisional mean
free path ~100 pc. Beyond the inner kpc region pressure torques drive the
angular momentum transport. In CCA, the BHAR is recurrently boosted up to 2 dex
compared with the disc evolution, which arises as turbulence is subdominant.
The CCA BHAR distribution is lognormal with pink noise power spectrum
characteristic of fractal phenomena. The rapid self-similar CCA variability can
explain the light curve variability of AGN and HMXBs. An improved criterium to
trace thermal instability is proposed. The 3-phase CCA reproduces crucial
observations of cospatial multiphase gas in massive galaxies, as Chandra X-ray
images, SOAR H$\alpha$ warm filaments and kinematics, Herschel [C$^+$]
emission, and ALMA giant molecular associations. CCA plays key role in AGN
feedback, AGN unification/obscuration, the evolution of BHs, galaxies, and
clusters.
