Ask HN: Important milestones for a startup

For a founder of a startup, it's a bit difficult to celebrate the important milestones since things are always going on and happening. (Who needs distractions?) I thought it would be a good idea to ask the HN community what are the important milestones that a startup/founder goes through along the way. Significance could be defined as relevant to the founder, important to the business, etc.

Here's something to get it started: MVP, First user, First customer, First hire, Funding

Edit: Comma-delineated the tentative list at the bottom