Actor and activist Christopher Reeve has died of heart failure after going into cardiac arrest.
Reeve was best known for his role as Superman in four hit movies.
In the 1990's, he was left paralyzed from the neck-down in a near-fatal horse riding accident.
After years of rehabilitation, Reeve returned to appear in several movies and TV shows. He also became an outspoken advocate of spinal cord research, and most recently, stem-cell research.