Blockchain technology has gained significant attention for its potential to revolutionize various industries by offering decentralized and immutable data storage and transaction mechanisms. This book chapter investigates the critical issue of blockchain interoperability and evaluates various solutions proposed to address this challenge. The chapter begins by providing an overview of blockchain interoperability, highlighting its importance in realizing the full potential of blockchain technology. It discusses the limitations of existing blockchain networks and described the need of interoperability. The chapter delves into an in-depth analysis of different approaches to achieve blockchain interoperability. These include interoperability protocols such as atomic swaps, sidechains, notary schemes, hashed time locks and cross-chain communication protocols, as well as interoperability frameworks. Finally, this chapter underscores the significance of blockchain interoperability as a catalyst for the widespread adoption and integration of blockchain technology into existing infrastructures.