 In his cosmological X-ray surveys work, 
Brandt has been a leader in obtaining the most-sensitive X-ray 
surveys to date, including the Chandra Deep Field-North and the 
Chandra Deep Field-South.These have been used to 
explore the demography, physics, and ecology of typical 
growing SMBHs over most of cosmic history.They have also 
allowed the study of X-ray source populations in starburst
and normal galaxies out to cosmological distances.