Initial Public Offering (IPO)
Once you have set up your own company as a private company, or created a private subsidiary, you can take it public with an IPO.
An IPO does two things: it raises funds for the company, and in most cases it gives the company a higher market valuation than it had while private.

An IPO can be reversed. Buying back 100% of the shares lets you take the company private again — see Privatization.