 Unlike his German peers, Virchow had great faith in clinical observation, animal experimentation (to determine causes of diseases and the effects of drugs) and pathological anatomy, particularly at the microscopic level, as the basic principles of investigation in medical sciences.He went further and stated that the cell was the basic unit of the body that had to be studied to understand disease.Although the term 'cell' had been coined in the 1665 by an English scientist Robert Hooke, the building blocks of life were still considered to be the 21 tissues of Bichat, a concept described by the French physician Xavier Bichat.