From the late 90s through the present day, the pop world has been in many ways dominated by the work of Pharrell Williams and Chad Hugo. The production partners, known as the Neptunes, helped cement hip-hop as a mainstream force – not just through their work with the likes of Jay Z, Clipse, and other rappers, but by brining hip-hop-infused soundscapes to pop and R&B artists. But Williams and Hugo don't just work behind the boards. With Shae Haley, Williams and Hugo intermittingly perform as N.E.R.D., a rock-meets-funk-meets-hip-hop trio that returns this week with its first album in nearly seven years, No One Ever Really Dies. For those who associate Williams with his silly, feel-good hit "Happy," No One Ever Really Dies takes things down a darker and more topical route. It's also an excuse to look back on five of the Neptunes' landmark productions. Each of these songs continues to impact pop culture long after fading from the charts.

Kelis, "Milkshake"
Kelis tempered her sound in recent years. Her highly underappreciated 2014 album Food softens the sexual aggressiveness and opts for a more organic feel than her earlier, chart-topping work with the Neptunes, with whom she worked on a trio of albums spanning the late 90s and early 2000s. Combined, the Neptunes and Kelis set a template for modern R&B that reverberates today. It pivots from 90s-styled vocal-first R&B to more of a hip-hop and electronic-focused sound. Listen to the coarse and burrowing funk synth that paths its way around Kelis' sensual albeit assertive vocals on "Milkshake" and hear a dark take of R&B still favored by the likes of Rihanna and even Beyoncé, whose sparser recent efforts owes some debt to the spacious hand-drumming that defines the beat. But the star of this show is Kelis, who struts and vamps in such a way that would-be-innocent words make a listener blush.

Britney Spears, "I'm a Slave 4 You"
While the former teen pop star has her champions, the singer isn't necessarily known for sonic adventurousness. Instead, Britney Spears built her success largely on studio wizardry, collaborating with producers who use each new album as something of blank digital canvas. Spears turned to the Neptunes for "I'm a Slave 4 You," her lascivious ode to dancing that once and for all shed any innocence. The Neptunes have a blast, concocting a track that feels like a sci-fi-inspired take on early Prince (especially the latter's work with Vanity 6). In turn, Spears – her voice at its most fine-tuned – comes off more like Janet Jackson than Madonna. Spears' breathy whispers are woven into the beat, and perky electronic flourishes ping-pong around the verses, creating a contrast between dark and brighter tones. While the tune was cut in 2001, such playful sparseness remains in vogue, as evidenced by Taylor Swift's Reputation.

Gwen Stefani, "Hollaback Girl"
Here's an example of a song that, on paper, reads like it would never work. First, in Gwen Stefani, we have a singer primarily associated with pop-punk attempting a dance-pop makeover. Then there's the matter of the lyrics. Near the end of the track, Stefani shouts and repeatedly spells out the word "bananas" as if conducting a cheerleading routine. Silly? Definitely. Rooted primarily in hip-hop, the song once again shows off the Neptunes' love for sparseness, as the booming, drum-line-like beat solely gets accentuated with an understated guitar during the chorus – at least until the brass section arrives. "Hollaback Girl" serves as a hip-hop popcorn song, and unexpectedly delivered by someone once rooted in the punk scene. Depending on your level of cynicism, "Hollaback Girl" figures as either gutsy or calculated. But one thing is certain: It was a hit, reaching No. 1 on the U.S. singles chart in 2005.

Justin Timberlake, "Rock Your Body"
If longtime fans were surprised Stefani went to the Neptunes for a career reset, they shouldn't have been entirely shocked. After all, a couple years prior, in 2002, the production duo did wonders for Justin Timberlake's career, helping him instantly transition out of boy-band infamy and into a smooth, R&B-focused singer. This track was originally intended for Michael Jackson, who passed on it, allowing Timberlake to display his falsetto and dance moves while working with an arrangement that flirts with naughty but feels rather nice. A svelte, retro R&B cut, "Rock Your Body" infuses elements of disco and pastel-shaded electronics, a mix that recalls earlier songs from Jackson and even Stevie Wonder all the while maintaining a futuristic poise. A decade later, Williams, with Daft Punk, would use a similar formula for the hit "Get Lucky." But here, the Neptunes demonstrate how to get frisky with humor. "Bet I'll have you naked by the end of this song," Timberlake self-referentially sings, midway through the cut.

Jay Z, "I Just Wanna Love U (Give It to Me)"
Jay Z was already an established star by the time he hooked up with the Neptunes for 2000 album The Dynasty: Roc La Familia. Yet a No. 1 single on the rap charts had thus far eluded the future Mr. Beyoncé. With "I Just Wanna Love U (Give It to Me)" the drought ended. The Neptunes cushion Jay Z's ghetto-tough image, helping him craft a playful, dance-ready rap song that presents the artist as a mostly nice guy with a bad-boy edge. Sure, Jay Z gets rebuffed throughout the song. "I wish I never met her," he charmingly and awkwardly sings. Still, his flirting mostly consists of telling the woman of his affection she's after "karats," not love. The sentiments aren't 100 percent sweet, but the song accomplished its mission. Bolstered with a shuffling, funky beat, it showed Jay-Z could succeed at just about any style of hip-hop.