preformationism

thumb|upright|A homunculus inside a [[sperm cell, as drawn by Nicolaas Hartsoeker in 1695]] thumb|Jan Swammerdam, Miraculum naturae sive uteri muliebris fabrica, 1729

In the history of biology, preformationism (or preformism) is a formerly popular theory that organisms develop from miniature versions of themselves. Instead of assembly from parts, preformationists believed that the form of living things exist, in real terms, prior to their development. Preformationists suggested that all organisms were created at the same time, and that succeeding generations grow from homunculi, or animalcules, that have existed since the beginning of creation, which is typically defined by religious beliefs.