Nanoscience development affects almost every discipline of science, engineering, and technology. Not surprisingly, "the science of small" is also finding its way into science classrooms. In general, "nano" refers to a billionth of a meter--about 1/50,000 the width of a hair follicle. The term "nanoparticle" usually refers to small materials with a size of between 1 and 100 nanometers (nm). Because nanoparticles are so small, they have a greater surface-area-to-volume ratio, causing them to be more reactive than larger particles and useful for various applications. In this directed inquiry for chemistry students, the authors introduce contemporary nanoparticle applications that address the "Next Generation Science Standards" (NGSS Lead States 2013). In the investigations described, students explore titanium oxide (TiO[subscript 2]) nanoparticles as photocatalysts activated by the energy of ultraviolet (UV) radiation.