The star cluster Hodge 301 is 20 million to 25 million years old. Hodge 301 is home to many aging, red supergiant stars, indicating the cluster is older. Roughly 40 massive stars already have exploded as supernovas. The expanding wave of debris is slamming into gas ejected by stars in R136, creating a ridge of star formation between the two clusters. The fledgling stars are embedded in dense gas and cannot be seen.
30 Doradus is the brightest, nearby star-forming region and home to the most massive stars in our cosmic neighborhood of about 25 galaxies. The nebula is close enough to Earth that Hubble can resolve individual stars, giving astronomers important information about the stars' birth and evolution. 30 Doradus resides 170,000 light-years away in the Large Magellanic Cloud, a small, satellite galaxy of our Milky Way.
Image Credit: NASA, ESA
Explanation from: http://hubblesite.org/newscenter/archive/releases/2012/01/image/d/