Learning RoR with Railstutorial.
I've built this along the tutorial, with the exception that I did a tiny work-ahead by introducing this line:
<%= @user.microposts.first.content if @user.microposts.first %>
app/views/users/show.html.erb, allowing the user's page to load also if the user didn't yet create a post.
It's also live here: https://afternoon-scrubland-93108.herokuapp.com/, just in case.