Getty Images is the worlds largest stock image licensing company, it was founded in In 1995 by Mark Getty and Jonathan Klei.
In 2006 Getty paid US $50 million to buy istockphoto, although a controversial move at the time (microstock was still seen as some sort of 'industry killer') istock has gone on to produce an ever increasing proportion of Getty's annual profits. Some feel that Getty have wisely kept the istock brand at arms length from their main company and other macrostock brands.
Getty own several major macrostock brands including stockbyte, photodisk and digital vision.
In October 2008 Getty announced its intention to buy Jupiterimages (the stock image side of jupitermedia) for a reported US $96 Million, the deal was approved by shareholders on 20th Jan 2009. This gives Getty the Jupiter brand and also a large share in the the microstock agency stockxpert (and its accompanying free site sxc / stockxchng, as of 2015 freeimages.com). The future of SXP is somewhat uncertain, however following recent announcements by istock that they will be adding new premium image collection, I think that there is still room in the market for several styles of microstock library (bargain basement price, select premium quality, convenient subscription etc) even if such outlets are owned by the same parent or source from the same collection.
Knowing who is behind a microstock site is always useful information, as the microstock industry continuously evolves new sales avenues spring up for microstock contributors, typical examples being stockxpert images being made available for a premium price via photos.com. I can imagine more and more companies building massive archives of user contributed images and supplying parts of these archives either through their own sub-brands and outlet network or via 3rd party niche agencies.
Getty made headlines in the industry back in September 2008 when it announced that it would be sourcing a flickr collection, as of February 2009 they are now starting to invite flickr users to submit their images, this process is done by invitation only and the terms that the users must agree to are getty's standard RF and RM agreements.
In January 2016 getty anounced a deal with Visual China Group (VCG) where Getty would be the exclusive distributors of the former Corbis Image collection outside of China.
As of 2016 The Getty Images collection consists of almost 200 million creative and editorial images and videos, (excluding additional images from Corbis/VCG)