World Championships 2017: Usain Bolt & Mo Farah headline London event
Jamaican sprint great Usain Bolt and British distance legend Mo Farah will attempt to sign off with gold at the World Championships which begins in London on Friday.
The pair, who have 28 world and Olympic titles between them, will both retire from the track by the end of the season.
Elsewhere, Jamaica's Elaine Thompson and Dutchwoman Dafne Schippers renew their sprint rivalry, while Britain's Laura Muir will attempt a formidable 1500m-5,000m double.
With Bolt not defending his 200m title, 400m world record holder Wayde van Niekerk will attempt to double up and establish himself as one of the new figureheads for the sport.
Fellow South African Caster Semenya is also fighting on two fronts, stepping up to 1500m as well as attempting to regain the 800m title she won in 2009 and 2011.
The Championships begin on Friday, five years to the day since Great Britain won three Olympic gold medals in less than an hour on 'Super Saturday' at the same venue.