Quantum computers may still be years away, but the security challenge they create has already begun. Today’s encrypted data can be harvested and stored by attackers, with the possibility of decrypting it once sufficiently powerful quantum computers become available. This talk introduces post-quantum cryptography, explains the emerging quantum threat to today’s security infrastructure, and explores which data is already at risk from harvest-now-decrypt-later attacks. The key message is simple: organizations need to prepare now.