Ernst Haeckel (1834–1919) was a German biologist, naturalist, philosopher, physician, professor, and artist who made significant contributions to the fields of biology and evolution. He was a zealous advocate of Charles Darwin's theory of evolution and is renowned for his influential work in the morphology and classification of organisms, coining terms such as 'ecology' and 'phylogeny.' Haeckel's devotion to Darwinism was instrumental in its widespread acceptance in Europe. His book 'Freedom in Science and Teaching' provides a robust defense of the scientific method and educational freedom, arguing against dogmatism in science and education. It reflects Haeckel's conviction that science should be free of religious and political constraints, and it champions the idea that teaching should present the latest scientific advancements without censorship. Haeckel also published 'Art Forms in Nature,' a work that showcases his detailed and beautiful illustrations of life forms. His drawings captured the imagination of scientists and laypersons alike, emphasizing the artistic symmetry and organization found in natural organisms. Haeckel's literary style is characterized by its clarity, fervent scientific advocacy, and sometimes controversial stances on religion and philosophy of science. His work not only contributed to the study of evolutionary biology but also left a lasting impact on the visual arts and culture of his time.