Pair any of the following options with your favorite set of breathable sheets and prepare for a comfortable rest that is beyond cool. The trick to finding a super-cool pillow is selecting the right materials for both filling and shell. Here are the ones that sleep and bedding experts recommended to us: While synthetic materials like polyester can trap heat and counteract any cooling fillings, these natural materials tend to be more breathable: While everyone’s different, those who tend to sleep on their sides will want a thicker pillow that fills the gap between their head and mattress to promote spinal alignment. Stomach and back sleepers often find flatter pillows to be more comfortable and supportive. Vyas adds that it’s also important to think about your sensitivity to synthetic materials like memory foam. These can off-gas volatile organic compounds that can cause respiratory irritation or skin discomfort in some people. If you’re someone who gets a headache just thinking about that strong “new pillow” smell, you’ll want to opt for natural filling and shell materials like wool, latex, down, kapok, cotton, and silk. Not only are these less likely to cause irritation, but they also tend to be gentler on the planet. Hsu also appreciates that this pillow is adjustable and sleepers can add or remove filling until they find their ideal feel. Reviewers note that this makes it a great option for side sleepers, who need to get that “just right” firmness level—especially those who suffer from back or shoulder pain. The one thing we don’t love about this option is that its cover is made from a synthetic polyester mix. Some reviewers note that their wedge pillow arrived squished (i.e., not in a wedge shape) but are grateful for Brentwood’s helpful and responsive customer service. Another notable perk: While foam pillows can usually only be spot-treated by hand, this down option is also machine washable. Free and carbon-neutral shipping and returns make for a nice cherry on top of this sustainable option. Avocado is also a leader in the sustainability space, offsetting more carbon emissions than they generate and donating most returned mattresses to shelters.