Proteins are biological macromolecules that carry out functions crucial for living organisms. Proteins make thermodynamically possible and kinetically achievable all biochemical processes and in this way regulate and coordinate the birth, growth, nutrition, excretion, division, reproduction, and, eventually, death of the organism. Proteins are fundamental elements in the replication and transfer of the genetic information stored in DNA and RNA molecules, thus ensuring the survival of the species. Proteins are the main structural element supporting the shapes and the morphological complexity of the living world. Proteins transduct the chemical and neuron signals needed for the adjustment of the organisms to their ever-changing environments.