There are not many Polish scientists in the fields of physics and chemistry whose names are well known all over the world as Jan Czochralski. Apart from Mikołaj Kopernik, Maria Skłodowska-Curie, Marian Smoluchowski and Kazimierz Fajans, probably only Jan Czochralski has found a permanent place not only in the history of these sciences but also in the modern scientific terminology. Scientific areas, such as solid state physics, electronics and materials science, which created the foundation of modern technology, owe, at least in part, their progress and present position to him. His first discovery in the beginning of the 20^Ih century was rediscovered later in the middle of the century by American semi-conductor technology specialists who named his crystal pulling technique the Czochralski method. This secured for Jan Czochralski a remarkable position in modem science. It is important, therefore, to know who Czochralski was and his scientific achievements.