Monaco - Mo Farah and Dafne Schippers, arguably Europe's two biggest track stars, will hone their Olympic preparations with what promises to be two testing outings at Friday's Monaco Diamond League.
Farah, reigning Olympic gold medallist in the 5000m and 10 000m and defending two-time world champion in both events, will warm up for Rio, just three weeks away, with some speed work over 1500m.
It is an event he has run before, famously setting a European record of 3:28.81 in 2013.
Farah clocked 3:28.93 to finish fourth in the event at last year's meeting and another fast time looks a certainty as he goes up against the top Kenyan trio of three-time world 1500m champion Asbel Kiprop, world silver medallist Elijah Manangoi and Ronald Kwemoi.
Kiprop's winning time last season made him the third fastest man over the distance, with just Morocco's Hicham El Guerrouj and American Bernard Lagat, then running for Kenya, having gone faster.
Also in the field at the Stade Louis II this Friday are Algeria's Olympic champion Taoufik Makhloufi, Morocco's Olympic and world bronze medallist Abdalaati Iguider (respectively seventh and eighth fastest ever) and Norway's Ingebrigtsen brothers Filip, who recently won the European title, and Henrik, who claimed European bronze in Amsterdam last week.
Schippers claimed two golds on her home track in the Netherlands as she wowed her Dutch fans by scorching to the 100m title and running a second leg that ensured victory for the 4x100m relay team.
"It's a very good time and a national record. Now we are ready for more, for Rio. We always want more," Schippers said after the Dutch team won the relay in 42.04 seconds.
She did not race the 200m, the event she won at last year's Beijing world championships in a third-fastest time ever of 21.63 seconds.
Schippers will compete in the 100m in Monaco and will face stiff opposition from American Tianna Bartoletta, the reigning world long jump champion who will also compete in the 100m at Rio.
Also running will be Jamaica's seven-time Olympic medallist Veronica Campbell-Brown, who at 34 has run a season's fastest of 10.83 seconds, the same as Schippers.
A late withdrawal from the meeting is Frenchman Jimmy Vicaut in the 200m, the favourite's tag now falling to Alonso Edward of Panama and Jamaican Julian Forte.
Forte's in-form teammate Omar McLeod will race against French medal hope Pascal Martinot-Lagarde, who is joined by teammates Dimitri Bascou and Wilhem Belocian, and Hungarian Balazs Baji,the podium finishers in Amsterdam.
South African Wayde Van Niekerk, whose gold medal-winning 400m run in Beijing made him the fourth best performer over the distance, has made sprint history by becoming the first athlete to dip under benchmark times in the 100, 200 and 400m.
But he insists his focus this season is wholly on the one-lap race.
Having already clocked 19.94 seconds and 43.48 seconds in the 200 and 400m, Van Niekerk timed 9.98 seconds in the 100m in March to set an athletics first.
Over 400m in Monaco, the South African will be guaranteed a tester by Isaac Makwala of Botswana, American Tony McQuay and Machel Cedenio of Trinidad and Tobago.