Physics and Chemistry are branches of science that both study matter. Physics is involved with the fundamental principles of physical phenomena and the basic forces of nature, and also gives insight into the aspects of space and time. Physics also deals with the basic principles that explain matter and energy, and may study aspects of atomic matter by following concepts derived from the most fundamental principles. Chemistry focuses on how substances interact with each other and with energy (for example heat and light). The study of change of matter (chemical reactions) and synthesis lies at the heart of chemistry, and gives rise to concepts such as organic functional groups and rate laws for chemical reactions. Chemistry also studies the properties of matter at a larger scale (for example, astrochemistry) and the reactions of matter at a larger scale (for example, technical chemistry) The division between chemistry and physics becomes diffuse at the interface of the two branches, notably in fields such as physical chemistry, chemical physics, quantum mechanics, nuclear physics/chemistry, materials science, spectroscopy, solid state physics, solid-state chemistry, crystallography, and nanotechnology.