More decimals to Bitcoin Bitcoin USD price is increasing continuously; it is not impossible to imagine a day where we get 1 satoshi = 1 USD cent or even more, 1 satoshi = 1 USD.
In that scenario we have a problem, bitcoin micropayments will be impossible, even with Lightning Network.

I know it is possible to increase the decimal places of bitcoin, e.g. 1 BTC = 1 00000000 00000000 units. My question is, how it can be done?
The Bitcoin developers would have to hard fork the chain to allow it.
I also don't think Bitcoin can get that expensive. Your talking 1 BTC = $100,000,000. If that's the case, the Bitcoin market cap would be $1,670,673,700,000,000 (1.6 quadrillion dollars). There is no such figure of money similar to that in circulation.