Leipzig were away to last year's beaten finalists Tottenham Hotspur while Atalanta entertained perennial European contestants Valencia.
The odds were stacked against the German club that amazingly was formed as recently as in May 2009, at about the same time North Queensland Fury and Gold Coast United were preparing for their maiden participation in the A-League.
The Italian club, which is playing in its first ever Champions League with a budget as big as Burnley's, faced a similar uphill battle to stay in the competition after surprisingly coming through the group stage.
Few people gave the German and Italian novices any chance against two well established clubs but football has a way of making fools of those who dare predict logical outcomes in an oft illogical sport.
Leipzig comprehensively outplayed Spurs in London and will take a 1-0 lead to the Red Bull Arena thanks to a second-half penalty from striker Timo Werner.
Atalanta sprang an even bigger surprise when captain and playmaker Alejandro Gomez played a key role in a sparkling 4-1 demotion job on Los Che in Milan, the Bergamaschi's home away from home because their own stadium in nearby Bergamo does not meet UEFA standards.
The Meazza Stadium had not seen a home win in the knockout phase of the competition in seven years.The last time it enjoyed such a luxury was in February 2013 when AC Milan beat Barcelona 2-0 in the first leg of a round of 16 tie.
The eye-opening exploits of Leipzig and Atalanta that have been masterminded by respective coaches Julian Nagelsmann and Gian Piero Gasperini have given the elite competition that is dominated by the usual suspects a breath of fresh air.
Nothing tickles the ivories of the fans more than a 'Cinderella' story a la Leicester who thumbed their noses at England's big six and won the Premier League amid universal acclaim four years ago.
Which is why true lovers of the world game should root for these unfashionable teams as they go about showing off their qualities on the catwalk of that most fashionable of competitions, the Armani of club football if you like.
There is no argument about the high quality of football the Champions League regularly serves up via by such mega clubs as Liverpool, Manchester City, Real Madrid, Barcelona, Bayern Munich, Paris Saint-Germain and Juventus.
Leipzig and Atalanta are unlikely to carry off this Champions League but their bravery, spirit and positivity - they can play a bit too - has earned them many sympathisers. Make no mistake, they have every right to be among the elite and they are proving it convincingly.
They have reminded us that sometimes - just sometimes - you don't need squillons of dollars to make a mark at the big end of town.
