Today marks the 15th anniversary of the formal creation of Matroska. The project was created on Sourceforge on the 6th of December 2002.
A lot has happened since Matroska was just an idea of a multimedia format with some specs and no code. The small community project has become a major player over the years and his now used by millions if not billions of people. You can now play Matroska files on your TV, your phone, your computer, your Blu-ray player and even on YouTube which uses WebM, a derivative of Matroska, when serving VP9 video in Chrome and Firefox.
The format continues to grow with recent additions for HDR and 360 videos. It is currently standardized at the IETF in the CELLAR group alongside EBML (it's parent file format developed at the same time), FFV1 a lossless video codec, and FLAC the lossless audio codec.