At the University of Warsaw he was taught by Kuratowski who was teaching the first year calculus course that Marczewski attended. Kuratowski writes in :-
... during the first tutorials in that subject [calculus] he attracted my attention by his extraordinary ingenuity. The audience then was exceptionally large (about 300 persons), the largest in the pre-war period; Marczewski was the best.Kuratowski directed Marczewski's studies and gave him much personal attention. However it was two other mathematicians at the University of Warsaw who influenced Marczewski more than Kuratowski. These were Mazurkiewicz and Sierpiński who interested Marczewski in measure theory and related topics. Remaining at the University of Warsaw to study for his doctorate under Sierpinski's supervision, he submitted his thesis in 1932. He had remained interested in collaborating with Kuratowski and, in the same year as his doctorate was awarded, a joint paper by Marczewski and Kuratowski was published in Fundamenta Mathematicae.
This was the golden age of Polish mathematics. From very unpromising times up to World War I, with the recreation of the Polish nation at the end of that war, Polish mathematics entered a golden age. In 1936, at the height of this remarkable explosion of mathematical talent, Marczewski wrote (see for example ):-
Poland always possessed great individuals, who worked, often with success, for the many, and not infrequently for whole institutions and sometimes for whole generations. But now it has among its mathematicians not only outstanding individuals but also a numerous, organised group of people whole-heartedly devoted to creative scientific work; it has its own school of mathematics.Marczewski was right, but sadly time were about to change. With the German invasion of Poland in 1939 the intellectual life of the country was destroyed (or at least there was a concerted effort by the invaders to destroy Polish intellectual life). Marczewski was visiting Lvov when it was occupied by the German army and here, as throughout Poland, intellectuals perished. For example A Lomnicki, S Ruziewicz, and W Stozek were three mathematicians from the Technical University of Lvov who were shot by a German firing squad in July 1941.
Then Marczewski returned to Warsaw, but in the capital things were equally difficult. Mathematics lecturers at the University of Warsaw who died around this time included S Kwietniewski and A Lindenbaum in 1941 and S Saks murdered in November 1942. For much of the war Marczewski survived in Warsaw suffering great hardships. However, near the end of the war he was captured and sent to a labour camp in Breslau, as the Germans called the town, but Wrocław to give it its Polish name.
In Wrocław, Marczewski was a prisoner of the Germans while the Russian forces besieged the city. The German defenders of Wrocław continued to resist even after the fall of Berlin. On 6 May 1945 the Russian forces captured Wrocław and Marczewski was set free. Perhaps the rather surprising turn of events was that he decided to remain in Wrocław and throw himself vigorously into the rebuilding of the university and educational system there.
The most important outcome which Marczewski worked for was the setting up of a Polish university in Wrocław. This he achieved with remarkable speed. On 24 August 1945, only three weeks after the Potsdam Conference, the Polish government issued a decree to:-
... convert the University and Technical University of Wrocław into Polish state academic institutions.Lectures began at the new Polish University of Wrocław on 15 November 1945. In addition to Marczewski, who was appointed as a professor, Steinhaus was appointed as Dean of the Faculty of Mathematics, Physics and Chemistry. Marczewski later became rector of the University and served for four years in this role.
The Polish Mathematical Society was equally quick to set up a new Wrocław section. At its first meeting following the end of the war in October 1945 it passed a resolution:-
... to welcome delegates from the Society's new Section in Wrocław. The meeting considers the vigorous start of the Wrocław mathematical centre's activities, and the presence of its delegates not only as a manifestation of the return of the Western Territories to Poland, but also as a proof of the rebirth of Polish culture in those territories. The General Meeting considers it to be a matter of great importance that the Wrocław Section, under the direction of Professors B Knaster, E Marczewski, H Steinhaus and W Slebodzinski and in cooperation with the University and Technical University of Wrocław, should constitute one of the most active scientific centres radiating across the Western Territories.Marczewski founded the journal Colloquium Mathematicum in 1946 in Wrocław, and he was its editor-in-chief for 30 years. In 1948 the Polish Mathematical Institute was set up, based mainly in Warsaw but having divisions in other cities. Marczewski was proposed as Deputy General Secretary of the Mathematical Institute. He was a cofounder of the Wrocław Centre of Excellence in Mathematics.
We should end by making comments on Marczewski's mathematics. His main work was in set theory, general topology, and measure theory. In  there is a bibliography of Marczewski's publications including 94 mathematical and 47 other research publications.
In  Kuratowski discusses some of the mathematical contributions made by Marczewski:-
He obtained particularly interesting and frequently applied results on the duality between the notions of a set of the first category and a set of measure zero; and similarly - between a set with Baire's property and a measurable set. He also devoted much attention to analytic sets (Suslin sets), operation (A) and uniformization ... . The great universality, elegance and simplicity of his proofs is a characteristic feature of his papers.Kuratowski also paid this fine tribute to Marczewski:-
... he was a man of exceptional wisdom and exceptional kindness, which won him adherents and numerous friends.
Article by: J J O'Connor and E F Robertson