In October 2010, installation of Advanced LIGO began. At that time, collection of data in the sixth LIGO observation run (S6, in coincidence with the Virgo detector) drew to a close. De-installation of Initial LIGO and the installation of Advanced LIGO was initiated. We are making progress towards the construction and testing of the first optical cavities at both sites, partial realizations of full interferometers: a single 4km-long arm of one of the two Hanford detectors, and the short Michelson configuration at Livingston. Concurrently, we have retrofitted a squeezed light source on the second Hanford detector, for use in a standalone experiment Jan/Feb 2012. In this talk we review the status of LIGO, with an introduction to the search for gravitational waves and LIGO detectors, the state of current detectors, and the prospects for first detection and transition to observational gravitational wave astronomy.