So the innate immune system that begins to act immediately after infection it involves cells like macrophages, neutrophils and so forth. And then we have our adaptive immunity that develops over some period of time because it has to synthesize the plasma cells, the memory cells, as well as other cells such as helper T cells and cytotoxic T cells. Now, adaptive immunity can be split into two. We have artificial and we have natural and each one of these can be split into active and passive. So basically, during the process of vaccination, during the process of immunization, when we take a vaccine and we inject it into that organism, into that individual, we inject an inoculated form of that pathogen. And what that does is it gives us active immunity by not having to have to experience the same exact detrimental effect that we would naturally experience if we are infected in a natural way.