Professor S S Chen is regarded as the greatest geometer of his generation. For six decades, he has been a leader in the field of differential geometry. Born in October 1911 in China, he obtained his BSc from Nankai University in 1930, MSc from Tsinghua University in 1934 and PhD from the University of Hamburg in 1936. He has worked in Paris and at the Institute for Advanced Study in Princeton, Academia Sinica of China and Chicago University. In 1981, he proposed the establishment of the Mathematical Sciences Research Institute (MSRI), and became its first director until 1984. MSRI quickly became a highly successful institute and many credit Chern as a major factor.

During his long career, Chern has been awarded numerous honorary degrees and prizes. He was elected to the US National Academy of Science in 1961, and received the National Medal of Sciences in 1975 and the Wolf Prize in 1983. He is also a foreign member of many societies, including the Royal Society of London, Academie dei Lincei, the French Academy of Sciences and Academia Sinica of China.

Chern has been invited three times to address at the International Congress of Mathematicians. The Congress is held every four years and it is already unusual for a mathematician to be invited twice to give a plenary hour address.

After retirement from UC Berkeley, Chern became Director of the Nankai Institute of Mathematics. The Institute now has an excellent library, has become increasingly active in international exchanges, and has many well-trained younger members. In 1995, the occasion of the tenth anniversary of the Nankai Institute was celebrated with a highly successful international conference, attended by many well-known physicists and mathematicians.

Chern's mathematical interests have been unusually wide and far-ranging and he has made significant contributions to many areas of geometry, both classical and modern. Principal among these are:

• Geometric structures and their equivalence problems;
• Integral geometry;
• Euclidean differential geometry;
• Minimal surfaces and minimal submanifolds;
• Holomorphic maps;
• Webs;
• Exterior Differential Systems and Partial Differential Equations;
• The Gauss-Bonnet Theorem;
• Characteristic classes, etc.

Chern is now still very active in mathematical research. He tries to work in areas that he feels have a future, avoiding the current fashions. His recent interests have been Lie sphere geometry, several complex variables, and particularly Finsler geometry. He has over 150 scientific articles and books to his credit.

When asked why he doesn't slow down and take it a little easier, his stock "excuse" is that he does not know how to do something else.

I was born on October 26, 1911 in Kashing, Chekiang Province, China. My high school mathematics texts were the then popular books Algebra and Higher Algebra by Hall and Knight, and Geometry and Trigonometry by Wentworth and Smith, all in English. Training was strict and I did a large number of the exercises in the books. In 1926 I enrolled as a freshman in Nankai University, Tientsin, China. It was clear that I should study science, but my disinclination with experiments dictated that I should major in mathematics. The Mathematics Department at Nankai was a one-man department whose Professor, Dr. Li-Fu Chiang, received his Ph. D. from Harvard with Julian Coolidge. Mathematics was at a primitive state in China in the late 1920s. Although there were universities in the modern sense, few offered a course on complex function theory and linear algebra was virtually unknown. I was fortunate to be in a strong class of students and such courses were made available to me, as well as courses on non-Euclidean geometry and circle and sphere geometry, using books by Coolidge.

The period around 1930, when I graduated from Nankai University, saw great progress in Chinese science. Many students of science returned from studies abroad. At the center of this development was Tsing Hua University of Peking (then called Peiping), founded through the return of the Boxer's Indemnity by the U.S. I was an assistant at Tsing Hua in 1930-1931and was a graduate student from 1931-1934. My teacher was Professor Dan Sun, a former student of E.P. Lane at Chicago. Therefore, I began my mathematical career by writing papers on projective differential geometry.

In 1934 I was awarded a fellowship to study abroad. I went to Hamburg, Germany, because Professor W. Blaschke lectured in Peking in 1933 on the geometry of webs and I was attracted by the subject. I arrived at Hamburg in the fall of 1934 when K?hler's book Einf?hrung in die Theorie der Systeme von Differentialgleichungen was published and he gave a seminar based on it. In a less than two-year stay in Hamburg I worked in more depth on the Cartan- K?hler theory than any other topic. I received my D.Sc. in February 1936.

The completion of the degree fulfilled my obligation to the fellowship. It was natural to look forward to a carefree postdoctoral year in Paris with the master himself, Elie Cartan. It turned out to be a year of hard work. In 1936-1937 in Paris I learned moving frames, the method of equivalence, more Cartan- K?hler theory, and, most importantly, the mathematical language and the way of thinking of Cartan. Even now I frequently find Cartan easier to follow than some of his expositors.

I returned to China in the summer of 1937 to become Professor of Mathematics at Tsing Hua University. I crossed the Atlantic on the S.S. Queen Elizabeth and, after a month long tour of the United States, I crossed the Pacific on the S.S. Empress of Canada. The Sino-Japenese war broke out while I was on board and I never reached Peking.

During the war Tsing Hua University moved to Kunming in Southwest China and became a part of Southwest Associated University. Mathematically it was a period of isolation. I taught courses on advanced topics (such as conformal differential geometry, Lie groups, etc.) and had good students.

In 1943 I became a member of the Institute for Advanced Study; both Veblen and Weyl were aware of my work. During the period 1943-1945 I learned algebraic topology and fiber bundles and did my work on characteristic classes, among other things. The war ended in 1945 and I decided to return to China. Postwar transportation difficulties delayed my trip so that I did not arrive in Shanghai until March 1946. I was called to organize a new institute of Mathematics of the Academic Sinica in Nanking. The work lasted only for about two years. On December 31, 1948 I left Shanghai for the United States, again on an invitation of the Institute for Advanced Study. (See Weil's article in Volume I. Before leaving China I was offered a position at the Tata Institute in Bombay, then at a planning stage, which I was not able to accept. The offer must have come on the initiative of D. D. Kosambi, the first professor of mathematics at Tata, who knew well my work on path geometry.) I spent the winter term of 1949 at the Institute. During 1949-1960 I was a Professor at the University of Chicago.

In 1960 I moved to Berkeley where I became Professor Emeritus in 1979. Together with C.C. Moore and I.M. Singer I submitted a proposal to the National Science Foundation for a Mathematical Institute in Berkeley. It was granted and I became the Director of the Mathematical Sciences Research Institute in 1971-1984. After my retirement I started a mathematical institute at my alma mater, Nankai University, Tianjin, China. I am hoping that my last retirement will come soon.