Institutions may be formal or informal, informal institutions are largely organic meaning they emerge naturally out of some preexisting substrate whenever there is a function to be performed, whereas formal intuitions are typically more artificial being designed by some set of explicit principles. Formal intuitions are made explicit and are socially excepted functions, for example, the family unit is a socially accepted functional unit, which is made formal and explicit by the process of marriage, but we also have functions within society that are not socially accepted and are thus not made formal, but at the same time they do not go away, they simply persist in an informal fashion, prostitution might be an example here, the rules and roles to the workings of that institution are not made explicit and formalized, they remain latent. Likewise, the use of drugs like marijuana would be an informal institution in many countries.