Amazon is now bigger than Walmart

Amazon is now bigger than Walmart.

Based on market capitalization, Amazon, which began as an online bookstore, has now overtaken the retail giant.

Amazon shares exploded 15% in after-hours trading to as high as $567 per share after the company reported quarterly earnings that beat expectations on the top and bottom lines.

Based on the after-hours spike, Amazon's market cap is now worth about $264 billion. Walmart is worth $233.5 billion.

Looked at another way, Amazon grew by about $36 billion in the first half hour after its earnings crossed. For comparison, Twitter's market cap is $23.5 billion.

Here's how Amazon has traded over the past five years: