In 2007, Remi Despres, already famous for having designed Transpac–an X25 Network in the 80s, had the idea to customize 6to4 to make a protocol that a Service Provider could use to deploy an IPv6 Service over an IPv4 Backbone.
For a full overview of all the principle Transition Protocols, please refer to this blog:
And this video:
The first popular automatic tunnels were 6to4. 6to4 solved two problems, IPv6 addressing and automatic destination tunnel configuration. 6to4, Connection of IPv6 Domains via IPv4 Clouds, RFC 3056 was published in 2001. It was one of the first transitions to IPv6 protocols after the static tunnels and dual-stack.
It provided the reserved IPv6 prefix, 2002::/16.