Blockchains are not without their challenges. One major issue is scalability, as many current blockchain systems face difficulties in processing large amounts of transactions quickly. This can lead to delays and increased costs, particularly for applications requiring high transaction throughput. Another challenge is interoperability, as different blockchain networks may not easily communicate with one another. This fragmentation can hinder the development and widespread adoption of cross-chain applications. Additionally, security threats, such as 51% attacks, pose risks to the integrity of a blockchain system, necessitating constant advancements in security measures.