![Lesson 2: Let's understand on-chain and off-chain | 【PoL】The best place to start learning cryptocurrency and blockchain from scratch. Lesson 2: Let's understand on-chain and off-chain | 【PoL】The best place to start learning cryptocurrency and blockchain from scratch.](https://s3-ap-northeast-1.amazonaws.com/polservice-s3/img/curriculum/usecase/project04-03.png)
Lesson 2: Let's understand on-chain and off-chain | 【PoL】The best place to start learning cryptocurrency and blockchain from scratch.
![hOCBS: A privacy-preserving blockchain framework for healthcare data leveraging an on-chain and off-chain system design - ScienceDirect hOCBS: A privacy-preserving blockchain framework for healthcare data leveraging an on-chain and off-chain system design - ScienceDirect](https://ars.els-cdn.com/content/image/1-s2.0-S0306457321000431-gr3.jpg)
hOCBS: A privacy-preserving blockchain framework for healthcare data leveraging an on-chain and off-chain system design - ScienceDirect
![hOCBS: A privacy-preserving blockchain framework for healthcare data leveraging an on-chain and off-chain system design - ScienceDirect hOCBS: A privacy-preserving blockchain framework for healthcare data leveraging an on-chain and off-chain system design - ScienceDirect](https://ars.els-cdn.com/content/image/1-s2.0-S0306457321000431-gr1.jpg)