Cryptocurrencies such as Bitcoin and Ethereum have gained enormous traction in the last few years. The monumental increase in value of Bitcoin and other cryptocurrencies seems only to be topped by the hype and notoriety surrounding them. But at its core, the Blockchain -- the technology at the foundation of cryptocurrencies -- has very desirable properties such as integrity, resilience and transparency, which makes it appealing to a large class of decentralized applications. In this talk, I will discuss some of the foundational technology that underlies the Blockchain. I will follow this up with some of the open challenges in this space and my current research threads that overlap with them.