UTXO Stack structure framework: Nervos CKB team expanded a set of standardized BTC layer 2 construction scheme based on the RGB++ technology protocol, which is regarded as the most Native solution to integrate the BTC main chain expansion. Because the UTXO Stack structure inherits the simplicity and security of native BTC, it can be regarded as a relatively mainstream BTC layer 2 direction in the short term. Recent protocol upgrades to the RGB++ layer and the engineering implementation of the UTXO Swap provide the foundation for BTC ecosystem developers to expand the Bitcoin ecosystem based on the UTXO structure.