The Heroes are those who possess extraordinary powers beyond general human evolution. Most of these people have attempted to use their powers for good, but some have wielded them towards more negative goals, using them to steal, overpower, or murder others.
The primary theory behind their creation is that an enzyme or chemical that spreads across genetic lines grants them their powers. Among some, this chemical may have occurred as a result of evolution; however, it is revealed near the end of Volume Three that indeed, some have received their abilities due to human intervention using The Formula.
Dr.Mohinder Suresh has come to surmise that the powers are activated through adrenal glands, in the exception of Rapid Cellular Regeneration and Empathetic Mimicry, some have found ways to master their abilities and can activate them at will.