Cuddl Duds are thermals (long underwear) that are super soft, very warm, form fitting, and not at all like your grandmother's long underwear. These are not the typical waffle thermals that are thick, bunch up under clothes, and have crotches that are 3 feet below the waist. These are actually made to fit a woman's body! They come in crew-neck and v-neck styles, but the v-neck is pretty high and is still visible when worn in many of my sweaters. However a good scarf covers that right up. I purchase mine at Macy's (they are 50% off right now), but they are also available at places like Kohls and JC Penney and online. They also come in various varieties: Softwear, ActiveLayer (with moisture-wicking and temperature control properties to the fabric), ClimateSmart (temperature control), and Softwear Stretch (super soft and sleek).
I also found these boxed versions at Sam's Club and I have seen these same ones at Target. However, the quality of these is not as good as the Macys ones. These are not as soft, they are more polyester-y to the touch, and don't come in the same varieties as the other stores I mentioned above. These feel like a cheap microfiber fabric that is better than waffle thermals, but not as good as the others above.
Cuddle Duds come in black, white, and light pink solids, and some stores carry a few prints like animal print and stripes. I like the lace trim on the ones pictured above because they are a bit feminine, but I like the non-lace ones too because they look like normal clothing. My favorite style is ActiveLayer because it helps regulate temperature, especially when shopping and I am constantly in and out of the cold, and I like the Softwear Stretch ones because they are super soft and the bottoms even have a bit of a low rise so that they are perfect under my low-rise jeans. They don't bunch up under normal clothing and even look like normal clothes so if you wore a Cuddl Duds top and jeans nobody would know you were wearing a thermal top.
Cuddl Duds are a great investment for keeping warm as they are functional and ideal for layering. They are a bit pricey at around $30 per piece, but they are on sale practically everyone right now so they are affordable and VERY worth it. My only wish is that they would make a low-cut neck version so that I could wear them under more sweaters without having the neckline show.
Now all my friends use Cuddl Duds. Have you tried them?