Recent Developments in Gravitational Microlensing
  Twenty-one years after Bohdan's seminal paper launched the field of gravitational microlensing, it has radically diversified from a method narrowly focused on finding dark matter to a very general astronomical tool. Microlensing has now detected 12 planets, including several that are inaccessible by other search methods. It has resolved the surfaces of distant stars, served as a magnifying glass to take spectra of extremely faint objects, and revealed a number of surprising phenomena. I take a sweeping look at this remarkable technique, giving equal weight to its successes and to the tensions that are continuing to propel it forward. 
Andrew Gould