Ryosuke Cohen was born in Osaka in 1948. He studied pedagogics and has worked as an art teacher since 1974. His family name is conventionally romanised as Kōen; on the advice of a friend, he adopted the English spelling "Cohen" — the name by which he is now known across the global mail art network.

Cohen discovered mail art through the Canadian artist Byron Black. Drawn to the physical act of postal exchange as an artistic medium, he set about building a worldwide network of contributors — ultimately realising this vision through the ongoing project that would define his practice: Brain Cell.

Launched in June 1985, Brain Cell invites artists from around the world to send stamps, stickers, drawings or collages to Cohen, who assembles them into a single printed sheet and returns it to all participants. The project's name comes from Cohen's own description: "I titled it Brain Cell because the structure of a brain under a microscope looks like a diagram of the mail art network — thousands of neurons clinging and piling together, just like the network itself." With over 6,000 contributors from more than 80 countries and 1,200 editions, the project continues today.

In August 2001 Cohen began the Fractal Portrait Project, travelling to meet Brain Cell contributors in person — across the United States, Italy, Korea, the Netherlands, Belgium and the United Kingdom — making the invisible network visible through direct encounter.