What is the science behind animal testing?

Stage 1: Human Cells - Early tests are done on human cells grown in a laboratory. Scientists try out different concentrations of a possible new drug. They test it on different types of body cells with the disease. These tests check how well the chemical works against the disease. They also give data about how safe the drug is for cells. Stage 2: Animal Tests - If the drug passes tests on human cells, it is tried on animals. Animal trials are carried out to make sure the drug works as well in whole animals as it does on cells grown in the laboratory. Stage 3: Clinical Tests - If the drug passes the animal trials, then it can be tested on people, these tests are called clinical trials or human trials. They give scientists more data about the effectiveness and safety of the drug