Molecular structure refers to the arrangement of atoms within a molecule. It determines how the atoms are bonded together and the shape of the molecule, which influences its properties and behavior. For example, the structure of water, H2O, consists of two hydrogen atoms bonded to one oxygen atom, creating a bent shape that is crucial for its unique characteristics. Understanding molecular structure is essential in fields like chemistry and biology. It helps scientists predict how substances will react with each other. For instance, the structure of DNA is a double helix, which is vital for its role in storing genetic information and guiding the development of living organisms.