Here's what Volkswagen did and how the emissions scandal has hurt the company

Cars with the VW brand saw sales slip by 0.5% to 420,000 in the first quarter this year, according to the latest European data, the only car brand in the top 10 to experience a drop in sales.

As well as declining sales, the company is facing management turmoil and costly legal actions in the US.

All because of a piece of software that cheated diesel emissions tests in the US for seven years.

The software could identify when it was being tested and reduce harmful exhaust so it looked as if the cars met requirements, when in fact they didn't.

Volkswagen was caught by independent testing carried out by a clean-air advocacy group, The International Council on Clean Transportation, which tested the cars because it thought they were such a great example of how diesel could be a clean fuel.

Here's a rundown on what happened and when.