  CONCERTO (CarbON CII line in post-rEionisation and ReionisaTiOn) is a large
field-of-view (FoV) spectro-imager that has been installed on the Cassegrain
Cabin of Atacama Pathfinder EXperiment (APEX) telescope in April 2021. CONCERTO
hosts 2 focal planes and a total number of 4000 Kinetic Inductance Detectors
(KID), with an instantaneous FoV of 18.6 arcminutes in the range of 130-310
GHz. The spectral resolution can be easily tuned down to 1 GHz depending on the
scientific target. The scientific program of CONCERTO has many objectives, with
two main programs focused on mapping the fluctuations of the [CII] line
intensity in the reionisation and post-reionisation epoch (4.5<z<8.5), and on
studying galaxy clusters via the thermal and kinetic Sunyaev-Zel'dovich (SZ)
effect. CONCERTO will also measure the dust and molecular gas contents of local
and intermediate-redshift galaxies, it will study the Galactic star-forming
clouds and finally it will observe the CO intensity fluctuations arising from
0.3<z<2 galaxies. The design of the instrument, installation at APEX and
current status of the commissioning phase and science verification will be
presented. Also we describe the deployment and first on-sky tests performed
between April and June 2021.
