A starfish or Sea Star has the ability to regenerate or rebuild lost body parts. It can be formation of complete starfish from a lost limb or just the reformation of the lost limb itself. This process is called as regeneration, and may take up to several months or a year to complete.

Like most of the other organisms in which regeneration is possible, Starfish regenerates in three complex stages. These are:

1. Repair Stage: In this stage, the body repairs and heals the exposed, wounded area to prevent the risk of infection. Usually cell debris collects at the site.

2. Regeneration Stage: This is the stage where new body cells form and, hence, regeneration of lost parts is visible. A basic structure is evident after this.

3. Advanced Regeneration Stage: This is the final stage in which the body cells start to proliferate. Growth factors are released to control this mechanism.