In researching magnetic recording, used in hard drive storage, a trilemma arises due to the competing requirements of readability, writeability and stability (known as the Magnetic Recording Trilemma). Reliable data storage means that for very small bit sizes the magnetic medium must be made of a material with a very high coercivity (ability to maintain its magnetic domains and withstand any undesired external magnetic influences). But this coercivity must be overridden by the drive head when data is written, which means an extremely strong magnetic field in a very tiny space, but the size occupied by one bit of data eventually becomes so small that the strongest magnetic field able to be created in the space available, is not strong enough to allow data writing. In effect, a point exists at which it becomes impractical or impossible to make a working disk drive because magnetic writing activity is no longer possible on such a small scale. Heat-assisted magnetic recording (HAMR) and Microwave Assisted Magnetic Recording (MAMR) are technologies that aim to modify coercivity during writing only, to work around the trilemma..