Little Brother's Big Secrets
Valued at £80 billion, the UK's junior stock market is hyped as the most successful growth market in the world.
Government incentives - including stamp duty and inheritance tax breaks - mean that more ordinary UK investors are opting for the Alternative Investment Market (AIM).
Set up in 1995 to allow smaller companies to raise funds, AIM is a less-regulated alternative to its big brother, the main London Stock Exchange.
But it is no stranger to controversy.
Once labelled a "casino" by a senior US regulator due to its lax regulation, the market has been hit by a series of recent high profile scandals.
File on Four asks if this light-touch regulation poses a hidden risk for shareholders and if unscrupulous businesses are exploiting AIM to rip off ordinary British investors?
Producer: Alys Harte
Reporter: Simon Cox.