The major cause of magnification in a microscope is due to the refraction of light by lenses. Refraction happens when light travels through space with a changing index of refraction. The simplest of refraction cases happen when there is an interface between a uniform medium, a certain index of the infraction, and yet another medium with an index of refraction. Some media actually have an index of refraction that varies as position changes; as such, the light rays curve through the medium rather than traveling in the regular straight line.
This effect is what is responsible for mirages that are seen on hot days where the regular changing index of refraction of air causes the light rays to bend while creating the appearance of a specular in the distance. You should note that the microscope is a series of lenses that effectively take advantage of the nature of refraction, which ultimately results in magnification.
Despite being a natural phenomenon, biological magnification is often triggered by anthropogenic factors. Some of these include organic containments, agricultural and industrial wastes, pollution from plastics, and heavy metals from mining. The release of toxic substances and pollutants in the environment, such as the seas, air, and land, are problematic.
These practices result in the end product being the accumulation of toxins and harmful chemicals. The concentration eventually accumulates and gets absorbed by lower organisms in the food chains such as fish, earthworms, and plants. Agricultural pesticides and chemical fertilizers are highly toxic and often find their way into the soils, rivers or lakes, or seas through surface stormwater runoff. Organic containments, such as personal care products and pharmaceuticals, also cause harm.