^Yup, with those boy short underwear. 
Sometimes lingerie is about what is pleasing to the one wearing it, not necessarily anything else.
I received several incredibly scratchy and tasteless negligees when I was engaged. This item is very hard to buy for someone, although I would buy something carefully chosen for my daughter, niece, or close friend. I wear mostly Hanro nightgowns - their mercerized cotton is satiny and elegant, and also very comfortable against the skin. I can’t stand to sleep in synthetics, and silk satin has little give, so it is uncomfortable when it twists around the body during the night. Cotton has a little natural stretch and breathes enough to feel good.
I think sleeping in them is beside the point. 
But I agree, for sleeping, definitely cotton.
Those are nice, @Gourmetmom, but pretty pricey just for something to sleep in, IMO.
Gourmetmom, if you like cotton and Hanro, take a look at Calida. Their cotton is super soft and feels luxurious.
http://www.calida.com/int-en/women/sleepwear-loungewear?calida_filter_quality_label=1582#pTop
The brand has an interesting history:
I am familiar with Calida - H wears the undershirts and PJs. Also great cotton, but more utilitarian looking. I think the Hanro nightgowns are an ideal mix of sex appeal and comfort…well worth the money, IMO, since we spend so much time in bed.
La Perla also has some very elegant nighties - not as comfortable, though - this looks bridal to me:
LOL $400 for sleepwear. I must be on the wrong thread.
I hesitated to recommend La Perla because it is pricy, but HerRoom carries lower-priced Studio by La Perla line. This one might be too see through and scratchy, but it looks so cute and is on sale (although only a few left):
http://www.herroom.com/la-perla-19079-studio-elodi-chemise.shtml
Here is a very cute Hanro chemise:
http://www.herroom.com/hanro-7731-moments-spaghetti-chemise.shtml
Check your Saks emails. I got one with a link that lets me use the FF discount today.
You know what’s comfortable and inexpensive yet sexy? Sleeping in the nude.
I like the first one Gourmetmom suggested.
I also like the Calida boy shorts and Ts posted by BB.
Now that you all know my taste, feel free to give me lingerie. Otherwise, stick to a robe in a solid color.
Wow, do check your Saks e-mails. This one is only $55 at Saks!
http://www.herroom.com/hanro-7731-moments-spaghetti-chemise.shtml
^^^ I have that in blue and in white - soooo comfortable, and not too short. I’m on Saks now to get one for D! Thanks!
@Gourmetmom - Make sure to login through the link in your email! Otherwise, the price is $79.
Groan. I still resent the nylon “pretty” cream-colored nightgown and robe as an engagement gift from a group of women in my life. Never worn it. Not my style, fabric, color or anything I desired or would enjoy. Ditto all the clocks, platters, and vases that were not on my registry. Just awful stuff. Still, these people were dear to me and I thoroughly enjoyed my engagement and wedding celebrations with them.
Dy,
I hear you. I gave away items with price tag on them. In my old age, I just go return or exchange.
My Saks order arrived today! I am keeping all of it. The Hanro spaghetti strap chemise linked above in S is perfect, and so is the deeply discounted Cosabella in L. 
Kiddo is getting a Cosabella nightie in cats.
Oops. No links. They are all sold out at the moment!