Paul Villard discovered the gamma rays on February 9th, 1903 while investigating radiation of radium salt. He noticed that there where 3 types of rays. one stopped at the lead barrier that was know to stop the alpha ways but 2 other types got passed that. One was beta ways that were deflected of of a magnetic field. Gamma rays stayed in the magnet field.
All parts of the electromagnetic spectrum have a lower and an upper bound for each ray. Gamma rays have the highest frequency and shortest wavelength of the electromagnetic spectrum. Their lower bounds are 10^19 hertz and the upper bounds are still unknown.
What Gamma Rays do for Humans
Gamma rays are used in the removal of cancer cells by controlling the gamma rays with a magnet. They are able to destory the cancer cells with out taking cemo theropy. Too much of gamma rays can be very deadly though. The Hulk was the only exception to this rule.
We found out the the wavelength of gamma rays are so small that they can't truly be seen by anything. We also found out that the upper bounds of the gamma rays frequency hasn't yet been determined yet.