Liquid is a federated sidechain to bitcoin developed by Blockstream and run by a federation of exchanges and other big Bitcoin industry players. Amongst its many features it supports asset issuance. When you look at liquid transactions you can see inputs with an issuance field from time to time, but till now it was really hard to find these transactions since neither blockstream.info nor liquid.horse list issued assets. That's why I built a Liquid Asset Directory that lists all issuances and reissuances. It also gives you the raw, JSON encoded data in case you want to run your own analysis.