Sir Chris Hoy will be the first to cycle in the 2012 velodrome tomorrow (Tuesday 27 July), marking two years to the start of the Games in London.
Hoy will be joined by other sporting stars at London's Olympic Park, including American runner Michael Johnson and British basketball player John Amaechi.
Hoy will complete a lap of the infield in the velodrome, which he helped design. He told BBC Sport, "It's only two years since the Beijing Olympics and it has passed in a flash so I'm sure the next two years are going to pass really quickly too. The Olympics are always there at the back of your mind. It's the main reason why you train every day."
London mayor Boris Johnson will mark the two-year milestone by launching an appeal for 70,000 people to volunteer to work as everything from city guides to press officers at the Games.
More than one million people are expected to register their interest in the London Volunteer programme.