The collection consists of 23 lecture drafts, manuscripts and accompanying documents. Yukawa examined his ideas repeatedly and then summarized his thoughts on paper. Sometimes, he organized his idea on paper in order to deepen his consideration. He made changes a number of times to polish up each manuscript as if being a technical artisan in disguise of a physicist. His papers are written in beautiful cursive English handwriting. Interestingly, these papers show Yukawa’s idea-forming processes. Notes written by Yukawa’s co-researchers are also included in the collection.