Dr. Fumio Oosawa (10th Dec 1922 – 4th March 2019), a pioneer of single-molecule studies, made a series of lectures on statistical mechanics at a summer school run by the Society of Young Scientists in Biophysics in July, 1996. Based on the lectures, the original Japanese textbook was published in 2011. Since then, the English version has been expected to be published. The Biophysical Society of Japan now publishes the English version in a Special Issue of the Biophysics and Physicobiology (Vol. 18), which is an open access journal, by the Editorial Team for this Special Issue. In December 2021, the Preface and first Chapter 1 were published. Chapter 2 and later will be published soon one after another.