In this section it is intended to have a small redoubt on the knowledge in the tanning technique. Thus, in the “Encyclopedia” section, there is a series of compilation works referring to the theory of the leather tanning process from its initial state until it is transformed into finished leather for processing. In the “Environment” section we try with other information gathering works to bring the reader up to date on how to reduce the impact that the tanning process can cause on the environment. In the section “History” we review throughout the history of humanity and the treatment of leather as a companion of man throughout his career. In the “Miscellaneous” section we will try to present people who, thanks to their work, have allowed us to advance in the tanning process and who, possibly, without their help, we would not have been able to get to where we are. In “Stories of history” we will include a series of short stories that will collect anecdotes, topics of the antiquity of tanning, brief stories, ancient processes and other curious and easy-to-read facts. And lastly, in the “R&D” section we will try to include research works that have helped to clarify and improve the leather tanning process and its different articles.