IOTA

A "Tangle" chain not a BlockChain

Basically instead of a single linear chain, something more like a lattice? (Actually a "directed acyclic graph"). Which allows multiple streams of blocks to separate and come together.

Short overview : https://blog.iota.org/fully-decentralized-iota-explained-in-under-3-minutes/

https://files.iota.org/papers/Rate_Control_Algorithm_ICBC_May_2019.pdf

Now launched its fully decentralized version 2.0 tangle : https://blog.iota.org/iotav2devnet/

Visualize the Tangle : https://v2.iota.org/visualizer