The honeybee Apis mellifera has emerged as a robust and influential model for the study of classical conditioning, thanks to the existence of a powerful Pavlovian conditioning protocol, the olfactory conditioning of the proboscis extension response (PER). In 2011, the olfactory PER conditioning protocol celebrates 50 years since it was first introduced by Kimihisa Takeda in 1961. Here, we review its origins, developments, and perspectives in order to define future research avenues and necessary methodological and conceptual evolutions. We show that olfactory PER conditioning has become a versatile tool for the study of questions in extremely diverse fields in addition to the study of learning and memory and that it has allowed behavioral characterizations, not only of honeybees, but also of other insect species, for which the protocol was adapted. We celebrate, therefore, Takeda's original work and prompt colleagues to conceive and establish further robust behavioral tools for an accurate characterization of insect learning and memory at multiple levels of analysis.Classical conditioning (Pavlov 1927) is a form of conditioning in which a subject learns to associate a neutral stimulus (the "conditioned stimulus," or CS), which does not originally elicit a behavioral response, with a stimulus of biological significance (the "unconditioned stimulus," or US), which elicits an innate, often reflexive, response. Through this association, the originally neutral stimulus acquires the capacity to elicit a conditioned response.Decades of research on animal learning and memory have established some invertebrates (e.g., the sea hare, Aplysia californica, the fruit fly, Drosophila melanogaster, the honeybee, Apis mellifera) as standard models for the study of classical conditioning (Giurfa 2007b;Menzel et al. 2007). This success can be attributed to the fact that these animals can learn nonassociative as well as Pavlovian and operant associations and possess relatively simple nervous systems that allow retracing of these phenomena to the cellular and molecular levels in different kinds of laboratory preparations. Among these invertebrates, the honeybee, Apis mellifera, has emerged as a robust and influential model for the study of