Why is the previous close price different from current open price


I am experimenting with bars and I noticed that in my minute bars, the open price for one was different from the previous minute’s close price.
Does anyone know why?


Nonliquid asset and the market gapped would be my guess.

actually there is no such things as close or open price.
it is becoming more and more useless to check open/close.
if you check different data providers, you will see different OHLC prices.
there is after-market hours, and premarket hours.
and some brokers allow you to trade 24hr.s.