Start layering your littles with the kids' warm, breathable REI Co-op Lightweight Crew Long Underwear top. It features a made-to-move design and all of the comfy for a day of play.

Underwear TopsBase Layer Tops

Layer your little one with the REI Co-op lightweight long underwear bottoms for infants and toddlers. Designed for warmth, these bottoms are easy to pull on and absorb moisture as it comes.

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Layer your hiking pal with the REI Co-op lightweight long underwear bottoms for kids. Designed for warmth, these bottoms are easy to pull on and wick moisture for comfort.

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With its buttery soft feel and support that's like a gentle hug, the girls' Athleta Long Distance bra might be her new favorite for school, practice and play.

UnderwearSports Bras

Designed with soft, supportive fabric that's great for school, practice and playground time, the girls' Athleta Long Distance 2.0 bra helps young adventurers keep moving in comfort.

UnderwearSports Bras

Suit them up for cold epics in the kids' Icebreaker Merino 260 Tech Long-Sleeve Half-Zip Thermal top. This midweight base layer is designed for easy layering and temperature regulation on active days.

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Ideal for cold weather, the kids' REI Co-op merino midweight base layer bottoms are soft—not scratchy—naturally regulate temp and made with wool that's certified to the Responsible Wool Standard.

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Oh so soft and not itchy, the kids' REI Co-op merino midweight base layer top is an ideal first layer for cold weather. It naturally regulates temp and is certified to the Responsible Wool Standard.

Underwear TopsBase Layer Tops

Make your kiddo's base layer the warm, breathable, kids' REI Co-op Midweight Crew long underwear top and they'll play happily outside all day. It's great on its own for inside play, too.

Underwear TopsBase Layer Tops

Make your tot's base layer the warm, breathable, toddlers' REI Co-op Midweight Crew long underwear top and they'll play happily outside all day. It's great on its own for inside play, too.

Underwear TopsBase Layer Tops

The kids' REI Co-op Midweight Long Underwear Bottoms are warm and very good at wicking moisture, making them an ideal base layer for highly aerobic cold-weather fun, like skiing and snowshoeing.

Underwear BottomsBase Layer Bottoms

The toddlers' REI Co-op Midweight Long Underwear Bottoms are warm and very good at wicking moisture, making them an ideal base layer for highly aerobic cold-weather fun, like skiing and snowshoeing.

Underwear BottomsBase Layer Bottoms

Made from soft organically grown cotton fabric, the Reima Moomin Print Trygg onesie has an offset zipper for easy dressing and long rib-knit cuffs with extra room for growth.

UnderwearUnion Suits

Stripes or Moomin print? Both! The soft Reima Moomin Sovare babies' onesie is made from organically grown cotton with a cute reversible style and long rib-knit cuffs that have extra room for growth.

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