After such exciting encounters last week, fans will hope for the same in the remaining first leg matches.
Here's a list of four young players to watch on Tuesday and Wednesday.
David Alaba began this season without much playing time but has started Munich's last 13 league matches. He has also featured in the Champions League four times this campaign, scoring once.
Alaba is just 20 years old but has twice been named Austrian Footballer of the Year. While he started off his career as a midfielder, he has transformed into an attacking left-back over the past year.
Nine days ago, Alaba showed just how good he was when Munich took on Schalke in the Bundesliga. The 20-year-old was man of the match as he scored twice from left-back.
Against Arsenal, Alaba will have to focus more on defending. Theo Walcott is expected to start on the right and will be making runs throughout the match. It will be interesting to see how well the Austrian international can cope with the Englishman.
James Rodriguez made his return from injury last week at Beira-Mar. The Colombian had a hamstring problem in January, keeping him out of seven matches.
The 21-year-old has certainly been second best when compared to Porto's leading scorer Jackson Martinez but Rodriguez still has seven goals in 12 league matches.
In the Champions League group stage, Rodriguez was good throughout but didn't make much of an impact in the final three games. He only scored once in six matches, but it was a very important goal as it gave Porto a vital win against Paris Saint-Germain.
Porto face Malaga in the Round of 16. The Spanish side were strong defensively in the Group Stage but the combination of Rodriguez, Martinez, and Silvestre Varela may be overwhelming for the Spanish side.
Schalke haven't had a great season domestically. The German side sit in ninth place in the Bundesliga, an astonishing 27 points behind leaders Bayern Munich. In addition, Schalke have already been knocked out of the DFB Pokal.
Yet, they find themselves in the Champions League Round of 16. Schalke had a great group stage, staying unbeaten over the six matches and beating out Arsenal, Olympiakos, and Montpellier for the top spot.
On Wednesday, Jens Keller and his team take on Galatasaray in Turkey. Schalke's defense will have to be very much on form in this match.
Joel Matip and Christoph Metzelder will have the task of keeping out Didier Drogba. With Metzelder's lack of pace, it will be up to 21-year-old Matip to keep up with the Ivorian.
Stephan El Shaarawy has been superb this season. The Italian has arguably been AC Milan's most important player this campaign, scoring 15 goals and assisting three in 24 league appearances.
The 20-year-old is the Serie A's second top scorer, just three goals behind Edinson Cavani. In addition, El Shaarawy scored twice and assisted once in the Champions League group stage.
AC Milan were knocked out by Barcelona in last year's Champions League quarterfinal and have the chance to avenge their loss in this year's Round of 16.
Taking down the Blaugrana is nearly impossible, but it can be done. Barcelona's defense has looked weak many times this season and could be broken down by the likes of El Shaarawy, Bojan, and Giampaolo Pazzini.