What is USDC and USDT backed by?

Could you elaborate on the nature of USDC and USDT and what they are backed by? I'm particularly interested in understanding the fundamental mechanisms that support their stability and value. Are they pegged to any particular asset or are they reliant on specific technological advancements? Additionally, I'd like to know if there are any regulatory frameworks or institutions that oversee their issuance and management. Your insights would greatly assist me in gaining a comprehensive understanding of these cryptocurrencies.