Nanomaterials are defined as entities that have at least one dimension in the range of 10−9 m or 1 nm. Nanoparticles are the connecting link between the Quantum and the Newtonian world as they exhibit interesting quantum phenomena but at the same time are created and maintained by Newtonian forces. They have been in use for centuries, as early examples of nanoparticles can be seen from fourth century colored glass from Rome, or the famous “Lycurgus” cup that shows dichroitic behavior when illuminated with different light sources. Nanocarriers are nanoscale vessels for carrying drugs and other molecules to specific targets. Both nanoparticles and nanocarriers are synthesized by two main types of approaches. The “top-down” approach aims at synthesizing nanoscale materials by breaking larger, suitable materials to the nanometer range. On the contrary, the “bottom-up” approach aims at the manipulation of individual atoms and molecules to create a suitable nanomaterial. Both approaches have their merits and issues that will also be discussed. The synthesis can be through physical, chemical, or biological methods that give unique properties to the resultant product. Nanocarriers and nanoparticles offer a significant advantage over materials due to their high surface area-to-volume ratio and their manipulability in terms of functions. Therefore, it comes as no surprise that in recent years both have found success as treatment and drug delivery options for multiple diseases. Nanoparticles and nanocarriers are the future that awaits medical science, this chapter aims to introduce the reader to the fundamentals of nanoscience and draw a picture of how these small entities are bringing large changes in the ways we treat diseases.