This introductory chapter deals with a number of issues that show how the fluid behaviour in M G is indeed the common denominator for most of the M G (Material, Life and Engineering) sciences.

In recognition of the above, it is possible to define the M G relevance in terms of thermofluidynamic field distortions induced by gravity forces. The role of the fluidynamic equations, of numerical codes and of the O M A is highlighted when performing M G experimentation in different Microgravity Environments.