As of now, animal testing is the closest we can get when it comes to testing new medicines, vaccines or medical devices on a living subject before moving on to actual human subjects. This is due to the limitations in our current technology and mathematical methodologies which we use to simulate changes in a system. For example, in one of the BME 382, Simulink is used to simulate organ systems in the body; however, there are too many assumptions incorporated with this method because this computer-based models use mathematical functions/methodologies. And, these mathematical functions have restrictions of their own which becomes more complicated when put together in one system. But with the rise of various techniques in recreating/mimicking organs through stem cells, I believe animal testing will soon be a thing of a past.