Two days ago, I chatted with my friends on the Lightning Network and discussed a problem, obviously $BTC is the largest asset in the cryptocurrency field, but the ecology and application of Bitcoin have been tepid, and even compared with $ETH, ETH's DeFi TVL can do 30% of the entire DeFi ecosystem, while BTC, including all cross-chain packaging forms, adds up to less than 0.3%. That's because BTC hasn't really made its way into DeFi natively yet, and network restrictions are one of the reasons. Since the birth of ETH, Bitcoin has been seeking to cross-chain BTC to ETH, and there are many such products, the essence of which is to bring better liquidity and income to BTC, and bringing continuous income to Bitcoin is also the research direction of many small partners focusing on #BTCFi. Therefore, there are a lot of BTC layer 2 networks, hoping to make BTC "move" in the DeFi field while joining smart contracts, among which BOB @build_on_bob's idea is quite interesting, giving up the traditional layer 2 network concept, not TPS, nor cheap transfers, but so that BTC has a complete smart contract-based financial and programmable functions, using BTC as a settlement, trust foundation and security guarantee. DeFi assets, bridging, and account systems on BOB all have BTC at their core. It is hoped that we can build a layer-2 network that takes into account the security and stability of BTC and the hybrid class of smart contracts of ETH, and the technical path used is the way of native BTC + ZK Rollup + BitVM bridge, and the trust minimization of native BTC on BOB is realized through a custom BitVM bridge. Therefore, all of BOB's product designs are very simple, but behind it is the abstract encapsulation of complex mechanisms, and the core logic is to allow BTC to be dispatched, pledged, borrowed and circulated like ETH, without losing the security and nativeness of BTC itself, and the ultimate goal is to build a BTC self-custody, verifiable and manageable modern rollup. BOB's philosophy has also attracted the favor of institutions including Coinbase Ventures, Castle Island, Mechanism, Bankless, IOSG, Blockchain .com, as well as independent investors such as AltcoinSherpa, Ran (Crypto Banter), Coin Bureau, etc., hoping that BOB can achieve ideal results on this path.