  We present the latest results on CIB fluctuations from early epochs from deep
Spitzer data. The results show the existence of significant CIB fluctuations at
the IRAC wavelengths (3.6 to 8 mic) which remain after removing galaxies down
to very faint levels. These fluctuations must arise from populations with a
significant clustering component, but only low levels of the shot noise. There
are no correlations between the source-subtracted IRAC maps and the
corresponding fields observed with the HST ACS at optical wavelengths. Taken
together, these data imply that 1) the sources producing the CIB fluctuations
are individually faint with S_\nu< a few nJy at 3.6 and 4.5 mic; 2) have
different clustering pattern than the more recent galaxy populations; 3) are
located within the first 0.7 Gyr (unless these fluctuations can somehow be
produced by - so far unobserved - local galaxies of extremely low luminosity
and with the unusual for local populations clustering pattern), 4) produce
contribution to the net CIB flux of at least 1-2 nW/m^2/sr at 3.6 and 4.5 mic
and must have mass-to-light ratio significantly below the present-day
populations, and 5) they have angular density of ~ a few per arcsec^2 and are
in the confusion of the present day instruments, but can be individually
observable with JWST.

Astrophysics