So active immunity can be achieved either naturally through some type of exposure to that pathogen, for example, an infection, which is what we discussed earlier or we can actually induce active immunity artificially via process known as immunization. And immunization involves injecting something called vaccines into our body so what exactly is a vaccine? So, a vaccine is essentially this little test tube that contains some sort of pathogen inside that test tube. Now, the pathogen has been altered in some way or form. It has been inoculated. And what that means is we change that pathogen in the laboratory and we change it in such a way to ensure that it does not damage the body as severely as it would normally when we are infected by that pathogen in a natural way.