Atsushi Miyano (宮野 厚司 ,Miyano Atsushi) was a biochemist in the Black Organization and apparently Shiho Miyano and Akemi Miyano's father. Atsushi Miyano and Elena Miyano started or continued on the APTX 4869 research according to Vermouth. One or both of them worked on the project before Shiho Miyano took over. Both Elena and Atsushi died for some reason which Pisco called an accident while Shiho was young.
Atsushi was a “mad scientist” who was unpopular in the scientific community because his work and theories were not mainstream.Agasa was a distant acquaintance of Atsushi and had met him and his wife at conferences. Atsushi complimented Agasa on his inventions. Atsushi Miyano’s true appearance is unknown as he hasn't appeared in the manga. He was shown in shadow in the anime.
Atsushi Miyano moved out of his father's house thirty years ago to go somewhere for his research; he had found someone to sponsor his theory, and was moving to join a large research facility. Conan and Haibara think this is the Black Organization. He got married in this time period to Elena and then visited his father's house then occupied by his childhood friend and playmate Souhei Degima later with Elena when Akemi was 4-5 years old. It was said that he seemed to have something important to discuss with his friend. The visit occurred 20 years prior to the current timeline.
Bourbon said he met Atsushi some time before he died.
Contrary to the personality generally associated with the phrase "mad scientist", Agasa describes Atsushi as having been "a very polite man" and that he doesn't think Atsushi was suspicious.