The advent of contemporary nanoscience with nanocrystals (NCs) occurred in the 1980s and continues to this day. NCs, or nanometer-sized solid drug particles, have crystalline features and unique electrical, optical, and chemical capabilities due to their nanoscale dimensions. Nanocrystals, unlike other nanoformulations, do not require a carrier, reducing carrier-related toxicity. Nanocrystal formulations offer the advantage of dose reduction as they do not require the use of a carrier system for preparation, thereby decreasing the overall drug dosage. NCs can be developed by using both top-down and bottom-up techniques. They appear in a crystalline state, as the name implies, but may be indeterminate depending on the method of manufacture. NCs must be uniform in size, shape, internal structure, and surface chemistry. Nanocrystals have the potential to address challenges across various industries, including drug delivery for poorly soluble compounds, cosmetic research and products, biotechnology, and catalysis. It is found in some research that NCs help enhance the bioavailability of weakly water-soluble APIs, that is, BCS class II and IV drugs having low bioavailability due to their less hydrophilic nature. Primary uses in the biomedical sciences include increased solubility, enhanced bioavailability, targeted drug delivery, controlled release, regenerative medicine, herbal formulations, and bioimaging. This chapter presents a detailed overview of nanocrystal principles, basics, and tactics.