ATO may refer to:
The United States dropped nuclear weapons on the Japanese cities of Hiroshima and Nagasaki on August 6 and 9, 1945, respectively, during the final stage of World War II.
An atom is the smallest constituent unit of ordinary matter that has the properties of a chemical element.
In quantum mechanics, an atomic orbital is a mathematical function that describes the wave-like behavior of either one electron or a pair of electrons in an atom.
Atorvastatin, marketed under the trade name Lipitor among others, is a member of the drug class known as statins, which are used primarily as a lipid-lowering agent and for prevention of events associated with cardiovascular disease.
An atomic clock is a clock device that uses an electronic transition frequency in the microwave, optical, or ultraviolet region of the electromagnetic spectrum of atoms as a frequency standard for its timekeeping element.
Atomic-force microscopy (AFM) or scanning-force Microscopy (SFM) is a very-high-resolution type of scanning probe microscopy (SPM), with demonstrated resolution on the order of fractions of a nanometer, more than 1000 times better than the optical diffraction limit.
The Atom (Dr. Ray Palmer) is a fictional superhero appearing in American comic books published by DC Comics.
In western Christian theology, atonement describes how human beings can be reconciled to God through Christ's sacrificial death.
Atomism (from Greek ἄτομον, atomon, i.e. "uncuttable", "indivisible") is a natural philosophy that developed in several ancient traditions.