Why are the Bombers being investigated?
The Bombers have offered themselves for investigation by the AFL and the Australian Sports Anti-Doping Agency (ASADA) amid uncertainty over the legality of substances administered to players during the 2012 pre-season. They convened a media conference at short notice on Tuesday just as several news outlets were about to run with the story. Former Essendon utility Kyle Reimers had been interviewed and appeared on TV news bulletins on Tuesday night.

What are peptides?

Peptides are a compound made up of amino-acid molecules. There are several forms of peptides that are legal for athletes to take. But there are others that promote muscle growth and have similar properties to human growth hormone (HgH). There is much more uncertainty over the effects, and therefore, the legality of peptides in sports medical circles than there is with HgH.

What is HgH?
According to WebMD.com, HgH is produced by the pituitary gland, spurs growth in children and adolescents. It also helps to regulate body composition, body fluids, muscle and bone growth, sugar and fat metabolism, and possibly heart function. It is known to accelerate muscle growth and improve athletic performance. HgH is prohibited both in-and out-of-competition under the World Anti-Doping Authority (WADA) List of Prohibited Substances and Methods.

Who is Stephen Dank?
A sports scientist with a strong NRL background, particularly with Manly, he joined Essendon in 2011 as the club's head of sports science. He had a reputation for pushing the boundaries while at the Sea Eagles with respects to research and innovation, particularly with the use of calves blood and DNA testing. Manly declared in a statement on Wednesday that it had no issues with Dank in his time at the club.

Why did he leave Essendon?
He was an early casualty last year, as the soft tissue problems plaguing the Bombers became a major crisis. By the end of the season, more than half of Essendon's list had missed games because of soft tissue injuries.

What were Essendon players asked to sign?
Bomber players were reportedly asked to sign waivers that would absolve the club of any wrongdoing, although there is also speculation that they were merely confidentiality agreements so rival clubs would not learn what the Dons were doing.

Who are the other key players?
The role of Essendon's 2012 high performance manager Dean 'The Weapon' Robinson has also come into question. He engineered the fitness campaign that had the Bombers looking super-fit at the start of last season, only for the spate of soft tissue injuries to start taking effect. By the end of the season, Robinson's high-performance management role had been handballed to Danny Corcoran, a longtime Essendon identity and a close friend of coach James Hird. Robinson was reduced to the role of fitness coach, but was reportedly suspended by the club on Tuesday evening shortly after the Bombers went public with the story.

How did this come to light?
This story has been bubbling beneath the surface for more than a year. Brownlow medalist and football commentator Gerard Healy claims to have heard from sports medical sources more than a year ago that Essendon had been linked to peptides and that he had brought it to the attention of then AFL football operations manager Adrian Anderson at the time. Others have been digging around the story for several weeks and the club brought matters to a head on Tuesday afternoon, just as several news outlets were about to publish the allegations.

How does the ASADA process work?
The ASADA investigators will get to work immediately and every Essendon player and football department employee can expect to be interviewed in the coming days and weeks. There is no timeframe for when the investigation will be completed. If there are suspicions that the WADA code has been broken, an independent Anti-Doping Rule Violation Panel, made up of experts in the areas of sports medicine, sports law, clinical pharmacology, ethics and investigations will assess the information presented to them, including information provided by the athlete, and then decide whether to enter a player's details on to the Register of Findings (a formal record of decisions on anti-doping rule violations and associated matters) and whether to recommend a sanction to the sport. The players would be given the opportunity to have a hearing before a sports tribunal. It would then be up to the AFL to sanction the players or support staff.

What are the potential penalties?
Rugby union pair Trent Anderson and Mitchell Spackman both received two-year suspensions for their involvement with Growth Hormone Peptide 6 (GHRP-6). Anderson's sanction was possession and attempted use, while Spackman's was for attempted use.

Which other clubs are implicated and why?
Robinson worked at Geelong for several years and Gold Coast for one season before joining the Bombers. Both clubs have released statements claiming no knowledge of any wrongdoing during the periods when Robinson was in their employ, while offering full co-operation with authorities during these investigations.