An "angstrom" (symbol: Å) is a unit of length that is commonly used in the field of nanotechnology, molecular biology, and atomic-scale physics and chemistry. It is named after the Swedish physicist Anders Jonas Ångström, who made significant contributions to the study of spectroscopy and the understanding of atomic and molecular structure.
One angstrom is equal to 0.1 nanometers (nm) or 1 × 10^-10 meters (m). In other words, it is a very small unit of length, often used to describe the size of atoms, molecules, and the wavelengths of electromagnetic radiation such as X-rays and gamma rays.
The angstrom is particularly useful when dealing with structures at the atomic and molecular scale, where measurements are often in the range of a few angstroms. For example, the diameter of a hydrogen atom is about 0.1 angstroms, and the bond length between two carbon atoms in a molecule like benzene is approximately 1.4 angstroms.
Millimeter (mm): The millimeter is equal to one one-thousandth of a meter (0.001 meters). It is frequently used for very precise measurements, such as the thickness of paper or the diameter of small objects.