CORNERSTONE is an open-source, licence-free silicon photonics prototyping foundry and the UK's leading silicon photonics hub. Founded in 2014, CORNERSTONE was built on a simple but powerful belief: that groundbreaking technology should be accessible, collaborative, and transformative. CORNERSTONE’s open-source model lowers the barriers to innovation in photonic integrated circuits, giving researchers and innovators the freedom to design, fabricate, and test new ideas. Now evolved into the CORNERSTONE Photonics Innovation Centre (C-PIC) - the UK's dedicated Innovation and Knowledge Centre for silicon photonics - CORNERSTONE supports a growing ecosystem of over 100 partners across more than 25 countries. C-PIC offers flexible prototyping services, design consultancy, start-up support, training programmes, and innovation funding, with the goal of building a thriving pipeline of silicon photonics-enabled companies across multiple industry sectors.