We summarize observational results on the stellar population and star formation history of the Scorpius-Centaurus OB Association ( Sco OB2 ) , the nearest region of recent massive star formation .
It consists of three subgroups , Upper Scorpius ( US ) , Upper Centaurus-Lupus ( UCL ) , and Lower Centaurus-Crux ( LCC ) which have ages of about 5 , 17 , and 16 Myr .
While the high- and intermediate mass association members have been studied for several decades , the low-mass population remained mainly unexplored until rather recently .

In Upper Scorpius , numerous studies , in particular large multi-object spectroscopic surveys , have recently revealed hundreds of low-mass association members , including dozens of brown dwarfs .
The investigation of a large representative sample of association members provided detailed information about the stellar population and the star formation history .
The empirical mass function could be established over the full stellar mass range from 0.1 M _ { \odot } up to 20 M _ { \odot } , and was found to be consistent with recent determinations of the field initial mass function .
A narrow range of ages around 5 Myr was found for the low-mass stars , the same age as had previously ( and independently ) been derived for the high-mass members .
This supports earlier indications that the star formation process in US was triggered , and agrees with previous conjectures that the triggering event was a supernova- and wind-driven shock-wave originating from the nearby UCL group .

In the older UCL and LCC regions , large numbers of low-mass members have recently been identified among X-ray and proper-motion selected candidates .
In both subgroups , low-mass members have also been serendipitously discovered through investigations of X-ray sources in the vicinity of better known regions ( primarily the Lupus and TW Hya associations ) .
While both subgroups appear to have mean ages of \sim 16 Myr , they both show signs of having substructure .
Their star-formation histories may be more complex than that of the younger , more compact US group .

Sco-Cen is an important “ astrophysics laboratory ” for detailed studies of recently formed stars .
For example , the ages of the sub-groups of 5 Myr and \sim 16 Myr are ideal for studying how circumstellar disks evolve .
While no more than a few percent of the Sco-Cen members appear to be accreting from a circumstellar disk , recent Spitzer results suggest that at least \sim 35 % still have cold , dusty , debris disks .