In Chapter 3 the question of what to test was explored from the aspect of state in the development process-that is, material, component or device. In the chapters that follow this one, the primary concern will be issues of how to actually perform tests are explained in detail. But here the vital bridge between these is addressed-how to select actually individual items for testing (sampling) and how to prepare the items selected for the testing process (sample preparation). ISO 10993-12 addresses both these issues (and the selection and use of reference materials) in summary fashion.