During the last decade, huge improvement in nanobiotechnology and nanomaterials production resulted in different forms of nanoparticles (NPs) with a huge potential for health-related applications that remain understudied. Such applications extend beyond a direct human effect and could be mediated via impacting the environmental conditions, livestock production, and even the outbreak of certain diseases. Evidently, the increased growth in the production of such nanomaterials along with their understudied effects/ potential on human health represents a major side effect of nanotechnology. Such limitations include not fully identified bio-distribution and the physiological/ toxicological impacts on the different body organs as well as cellular activity upon exposure. NPs are very small in size (1 to 100 nm) and are found in different forms. There are various classifications of NPs depending on their size, shape, and properties. NPs have special physical and chemical characters as a result of possessing a large surface area and nanoscale size. The lack of proper safety assessment studies of such NPs, both in vitro and in vivo, as well as the shortage in biodistribution/ adverse effects and mechanisms represents a major concern. This brief review attempts to outline and correlate reports on several NPs and their application in the medicine and biology as well as summarizing any discrepancies in experimental conditions, toxicity, biohazard, and safety of NPs in different organs.