Friend-focused photo sharing app Retro snags $21M

What happened
Retro, a friend-focused photo-sharing app built by former Instagram employees, has raised more than $21 million in Series A funding.
Summary assembled by rule from the sources below

Retro, a friend-focused photo-sharing app built by former Instagram employees, has raised more than $21 million in Series A funding.
Summary assembled by rule from the sources below