By now, Ronda Rousey has made the leap from UFC star to crossover superstar. She's everywhere, especially in the week before she fights.

Such as been the case during the lead-up to UFC 190 on Saturday night in Rio de Janeiro, Brazil, where the UFC bantamweight champion will defend her title for the sixth time.

Less is known by the public at large about the challenger, Bethe Correia. But that's common among UFC women's bantamweights, with the possible exception of Miesha Tate. Casual fight fans just don't know this division as well as they might, say, light heavyweight.

So for fans who want to familiarize themselves with the "Rousey-weight" division, here's a primer on all the names worth knowing. For convenience, they've been sorted into five descending tiers.

 

Champion
Ronda Rousey (11-0, 5-0 UFC)

Rousey's dominance precedes her. She has finished every bout of her MMA career -- professional or amateur -- and been pushed beyond the first round on just one occasion. Just three of her fights have lasted longer than 76 seconds. Rousey holds wins over all of the below True Contenders as well as half of the Upper Echelon.

The former Olympian's as-yet unstoppable judo throws and quick armbar transitions are her bread and butter, but a rapidly improving striking game will make opponents wary of trading punches, kicks, knees and elbows.

 

True Contenders
Alexis Davis (17-6, 4-1), Miesha Tate (17-5, 4-2), Cat Zingano (9-1, 2-1)

Davis and Zingano lasted a combined 30 seconds against Rousey in the champ's last two fights, and Tate has lost twice via armbar to the division's queen. That said, these are still the definitive top 135-pound women in the world.

All three are well-rounded, but none of them is all-world in any one skill. Tate's four-fight winning streak and broad appeal appear to have put her next in line for a third crack at Rousey. It's worth mentioning, however, that Zingano beat Tate in their only meeting in April 2013. It's certainly possible that Davis and Zingano will earn second chances someday, too.

 

Upper Echelon
Bethe Correia (9-0, 3-0), Jessica Eye (11-3, 1-2), Sarah Kaufman (17-3, 1-1), Sara McMann (8-2, 2-2)

McMann and Kaufman each faced Rousey and met similarly lopsided results. Correia gets her chance on Saturday, while Eye missed out on a possible title shot when she lost to Tate on July 25.

Of the four, McMann would seem to have the most room for growth and a chance to one day usurp the champ. She's an Olympic silver medalist in wrestling, although the rest of her game leaves much to be desired.

Kaufman once reigned over this division before Rousey's arrival, but she has fallen on hard times since.

Correia may be unbeaten, but she doesn't have any wins over the other 16 women on this list. Her title shot came as a product of her perfect record and penchant for self-promotion. A poor showing against Rousey likely pushes her down to the next group.

Eye's most impressive showing was a win over Kaufman that was later overturned by a failed drug test. She, too, could fall from this perch if she were to lose again.

 

Muddled Middle
Liz Carmouche (10-5, 2-3), Holly Holm (9-0, 2-0), Lauren Murphy (8-2, 0-2), Rin Nakai (16-1-1, 0-1), Amanda Nunes (10-4, 3-1)

Holm has yet to impress after making the leap from world boxing champion to MMA, but with time she could become one of the division's best.

If Nunes hadn't faded in a loss to Zingano, she might already be among the elite. There's still time for her to get there and one day fight for the title.

Carmouche has been there and done that already. She lost to Rousey in the UFC's first women's bout back in February 2013. She's the epitome of an upper-level gatekeeper -- if you can beat her, you are quite a fighter.

Nakai and Murphy have yet to win in the octagon, but their pre-UFC resumes place them among this group of fighters. But if they don't win in their next respective outings, they're likely to fade into near irrelevance.

 

Best of the Rest
Jessica Andrade (13-4, 4-2), Germaine de Randamie (5-3, 2-1), Julianna Pena (6-2, 2-0), Marion Reneau (6-2, 2-1)

Pena, 25, and Andrade, 23, are prospects. It's possible they will develop into elite fighters someday, but they remain on the outside for now.

Reneau and de Randamie, on the other hand, are simply experienced fighters who won't sniff the title picture anytime soon.

 

Outside the Octagon
Tonya Evinger (15-6), Cristiane Justino (14-1), Pannie Kianzad (8-0), Agnieszka Niedzwiedz (7-0)

Justino, better known as Cyborg, is every bit the terror Rousey is. However, she fights at 145 pounds and has long resisted cutting the extra 10 pounds to meet Rousey at bantamweight. If she were to ever make the long-awaited but challenging move to 135, a Rousey vs. Cyborg matchup is the most interesting women's fight conceivable.

Evinger is riding a seven-fight winning streak, and her only losses over the last eight years have come against Davis (twice) and McMann. She likely ranks among the Upper Echelon of UFC bantamweights.

Kianzad, 23, holds an October 2013 decision victory over current UFC bantamweight Milana Dudieva and has three wins by TKO. Niedzwiedz is just 20 years old, and all but one of her victories went to a decision. Both are prospects who may belong in the same breath as Pena and Andrade.