Behavioral neuroscience commonly uses several models of a single disease such as depression. This multiplicity takes two forms. Mosaicism of models refers to the multiplicity of hypotheses explaining one disease: many different theoretical models supposedly refer to the same integrated mechanism but the way to do that remains undetermined. Chimerism of models refers to the multiplicity of animal models realizing one hypothesis: it is not and cannot be tested as a whole, but has to be experimentally implemented subpart by subpart through many representational models, i.e. three-dimensional instantiations of a theoretical model. Mosaicism and chimerism of models in biomedical science point to the necessity and difficulty of integrating pieces of information