In 1784, a small book entitled Essai d'une Théorie sur la Structure des Crystaux was published marking the beginning of modern crystallography. A crystallography that departs from being purely descriptive to using mathematics. A crystallography that predicts shapes and reveals molecules that would be debated for almost a century. Its author, René-Just Haüy, a French abbot living in Paris, at almost 40 years old, began a scientific career focused on the study of crystals. His successes made him one of the greatest scientists of his time. To mark the bicentenary of his death, this article presents the milestones of his unusual career in the troubled historic context of the end of the 18th century. The state-of-the-art knowledge of crystallography before Haüy is demonstrated. Then, Haüy's work is highlighted from the birth of a myth to that of a theory that made crystallography and mineralogy real sciences like physics and chemistry. Finally, without neglecting the criticisms of the German scientists, the heritage of Haüy's theory is developed with the works of Delafosse and Bravais.