A lie-to-children (plural lies-to-children) is a simplified explanation of technical or complex subjects as a teaching method for children and laypeople. The technique has been incorporated by academics within the fields of biology, evolution, bioinformatics and the social sciences. It is closely related to the philosophical concept known as Wittgenstein's ladder. A typical example of this is found in physics, where the Bohr model of atomic electron shells is still often used to introduce atomic structure before moving on to more complex models based on matrix mechanics; and in chemistry, where the Arrhenius definitions of acids and bases are often introduced, followed (in a manner similar to the historical development of the model) by the Brønsted–Lowry definitions and then the Lewis definitions.