With fervor returning to the crypto markets, industry executives are calling the start of a new bull run, mainly predicated on two things — the bitcoin “halving” and the potential approval of a bitcoin exchange-traded fund in the U.S.

The halving, which happens every four years, is an event written in bitcoin’s code. The rewards so-called miners get for mining bitcoin is cut in half. This keeps a cap on supply of bitcoin, of which there will only ever be 21 million. In previous price cycles, halving preceded a rise in the price of bitcoin.