Layout breaks in Polymer

Hi all,
I’m building an app in Polymer and I’m trying to implement Plotly.JS, but somehow the whole layout breaks. I tried to set fixed height/width for the parent div, target div and also tried to give width/height parameters to my layout object. In all cases I’m getting the following result:

I’m trying to fit the chart in the white block, all the gray is my background
I copy pasted the example from here
I also removed all my previous CSS but everything is still displaying below each other.

Where to start?

A reproducible example would help. It’s very hard to debug from screenshots