The fastest and most intense domestic swim meet until Omaha 2020 has a slightly misleading ambiance, conducted under tranquil and calm California sunny skies.

Four years ago, at this same outdoor Phillips 66 National Championships, I sat poolside and reflected on this unique paradox: Finals had just ended, and the white natatorium lights enshrined the azure waters against the warm California night. It was an odd mix of pressure and nostalgia, one of fun infused with intensity. For me, these Summer Nationals not only make me cheer like a maniac, but also evoke childhood nostalgia. I think of summertime poolside antics, Marco Polo games, and 25 sprints for no prize nor podium, only pride.

The only difference is, these sprinters at the Phillips 66 Nationals are the best summertime sprinters in the land.

This next week in sunny Irvine, California will aim to not only showcase the nation’s best swimmers, but also make its participants reflect and ponder both one’s past as well as one’s future. While these races have major implications and incentives — Pan Pacific Championship roster spots, National Team selections, national titles, mid-Olympiad momentum — for many swimmers, this week is both a culmination and a crossroads. It ends a year of training, and it also begins a march towards Omaha.

Often, the direction towards Nebraska can be laden with winding roads. For those athletes who take titles this week and swim on to Tokyo and the Pan Pacs, the road to 2020 looks straighter and more certain. Others may have to re-route their plans and make adjustments.

But make no mistake: There is no turning back now.  This summer's Nationals is just one stop on the way towards that SwimMecca among the vast Nebraskan corn fields, towards another natatorium that isn’t all sunny skies and summertime nostalgia, but the ultimate sprint from the blocks… one that decides our Olympic roster.

For now, for this week, it’s a mix of emotions and feelings, of fun and intensity. And for those lucky enough to sit poolside like I did four years ago, or for those of you following along from afar, here are your Five Storylines To Watch this week…

5. The women and men’s 100 meter freestyles…

Most international roster squads feature more swimmers from this event than any other, which is why the sprint 100 freestyle is always an “event to watch.” So many big names and veteran swimmers are vying for these two events. Don’t blink. On the women’s side, Simone Manuel is the front runner and person-to-beat, but she’ll have her hands full with Mallory Comerford, Lia Neal, Margo Geer, Kelsi Dahlia, Olivia Smoliga, Allison Schmitt, and can-do Katie Ledecky. Meanwhile, on the men’s side, no one will touch freestyle phenom Caeleb Dressel. But after Dressel, there are eight swimmers seeded within a second of each other, including Olympic gold medalist Nathan Adrian, Zachary Apple, Townley Haas, Blake Pieroni, and Ryan Held. There are also a few Olympic gold medalist backstrokers in this event, Ryan Murphy and Matt Grevers. Though each event feature favorites, anything can happen in this sprint-to-the-wall-and-back event.

4. Men’s 200 fly: Life without M.P.

We United States swim fans have been blessed with incredible fortune watching one of our sports greatest swim the 200 fly, year after year. No longer. Who will take the 200 fly domestic throne? I love watching this event come down to the final five meters, because every swimmer is doing everything he can to hang on and make it to the wall. Every 200 fly is about survival, and who can survive the longest. Jack Conger, Chase Kalisz, Pace Clark, Gunnar Bentz, and Tom Shields could all survive long enough to take the top podium spot. Though I wouldn’t necessarily be disappointed if Michael Phelps snuck in as a ringer, just for old time’s sake…

3. Women’s 100 breast.

One of the most fun swimmers to watch in 2016 was Lilly King. She swam the way coaches want their swimmers to swim: Fierce and swimming to win. Now, King owns the world record in the sprint event and looks to solidify herself as one of the sport’s greatest breaststrokers ever. Could others take her down this meet? I doubt it, but you never know. Katie Meili has certainly consistently dropped time over the years. I could see this event going down to the final ten meters. But it would be hard to bet against The King.

2. Men’s 100 back.

Oh, I’m looking forward to this one. Ryan Murphy, defending Olympic gold medalist, will take on another Olympic gold medalist and veteran Matt Grevers, as well as Jacob Pebley and Justin Ress. You know Grevers is looking to make that Pan Pacs team. You know he’s been looking forward to this race for a long time. And you know that Murphy knows what winning takes. And you know that Pebley and Ress are hungry to upset both swimmers. It’s sad that only two swimmers from this crowded field will make the Pan Pacs roster. Which is what makes this event so enticing.

1. Katie Ledecky and the hunt for more incredible world records…

Last season, the NBA was caught up in a debate if LeBron James is the greatest all-time basketball player, even better than Michael Jordan. I feel like we’re veering towards a similar swim-fan debate with Ledecky and Phelps. I am often not in the game of click-bait comparisons, but it’s hard to not point towards the jaw-dropping dominance of Ledecky and say, “We are witnessing something we’ve never seen before.” Could she break even more world records this meet? My guess is yes, because I’ve learned that Ledecky can break world records at a Marriott hotel pool. I’d also wager that Ledecky is aiming to do her best performances at Pan Pacs. Either way, don’t miss anything Ledecky swims this week. Because before you know it, it’ll be history.