It is one of several Breakthrough Initiatives [1] established by Julia and Yuri Milner. Breakthrough Starshot [2] aims to send a fleet of extremely small probes to Alpha Centauri in a flyby mission.

(Another initiative, Breakthrough Enceladus, would send a probe to the Saturn moon but I cannot find information about whether this is an active ongoing effort.)

[1]: https://en.wikipedia.org/wiki/Breakthrough_Initiatives

[2]: https://breakthroughinitiatives.org/initiative/3