Fibers fill. Sprays lift, and that is a different job. Before you pile anything on, a root spray can make fine hair stand up so there is less to cover.

RŌZ makes two in this row. AIR Thickening Spray comes from LA stylist Mara Roszak and is made with sandalwood, mushroom and rice extracts. You can spray it on damp hair and blow-dry for volume, or air-dry for subtle lift. ROOT Lift Spray goes on damp roots, and the tip is to flip your head upside down while you blow-dry. Philip Kingsley Density Thickening Protein Spray is heat protecting and made with hyper-branched polymers and hydrolyzed pea peptides. R+Co Bleu Magnifier Thickening Spray adds pea proteins and biotin, and Oribe Maximista Thickening Spray gives medium hold and is color and keratin treatment safe.

For roots, Hair by Sam McKnight Cool Girl Superlift goes on before blow-drying, and Moroccanoil Root Boost is a spray-on mousse for towel-dried roots and a round brush. OUAI Thickening & Volume Spray is the one sold for flat, thinning hair, with an amaranth peptide.

Pairing tip: spray the roots, blow-dry, finish styling, and only then use fibers.

What I would skip: mousse or a heavy spray right on top of fibers. Keep the lift at the root and the fibers on the surface.

Serums work on a slower clock, and every brand here words its promise carefully, so I will too. None of these is a quick cover-up.

Vegamour GRO Hair Serum is a vegan dropper serum with turmeric and caffeine, and Vegamour says it gives thicker-looking hair in as soon as 90 days with daily use. The Ordinary Multi-Peptide Serum for Hair Density is made with Redensyl, Procapil and Baicapil, and the directions are a few drops on a clean, dry scalp at bedtime. Augustinus Bader The Scalp Treatment is built around the brand's Trigger Factor Complex, and the brand says it was created for thinning, damaged or weak hair.

Philip Kingsley Density Preserving Scalp Drops say they are designed to help maintain follicle condition, and they are dermatologically tested. Agent Nateur holi (growth) 84 is a leave-in with Redensyl and rosemary that the brand says targets visibly thicker hair in 84 days. Virtue Flourish Density Booster is a scalp spritz made for mild to moderate thinning, according to Virtue. Highbrow Hippie Root Replenish is a water-based serum you massage in for 30 seconds twice a day. Act + Acre Microbiome Cooling Scalp Serum is the soothing one, with peppermint oil and hyaluronic acid for a dry, itchy scalp.

What I would skip: switching serums every few weeks. Choose one, use it as directed and give it the time the brand names. If your thinning is sudden, a doctor is a better first stop than any bottle.

Start with color. Fibers that match your hair disappear, and ones that are a shade off look like a stain. Toppik sells Hair Building Fibers in nine shades, so check the brand's shade range against your roots in natural light before you commit.

Then keep the routine short. Serum in the evening, a root spray on damp hair, blow-dry, fibers last, a light mist of FiberHold on top. The brand says the fibers resist wind, rain and perspiration, and that Hair Filler stays until you wash it out. Keep the fibers away from your eyes, as the brand tells you to.

If you are using a scalp serum, give it the weeks the brand names before deciding whether it suits you. The fibers make the look of your hair fuller today. Everything else in this page helps the hair you have, and one of those jobs is much faster than the other.

If Toppik fibers are the last step in your routine, the first step is a wash that already leaves roots lifted. I start with shampoos. Crown Affair's Volumizing Shampoo uses rice protein and coconut-based surfactants, and its conditioner adds hyaluronic acid and panthenol. Philip Kingsley Density Thickening Shampoo has hyper-branched polymers that push hair apart as it dries, and Kérastase Densifique is built on hyaluronic acid for thinning hair. Caudalie's Hair Volume Shampoo is sulfate-free and silicone-free, Fable & Mane uses fenugreek seed, and OUAI's Fine Hair Shampoo is a color-safe gel with biotin.

For between washes I reach for dry shampoos. R+Co Bleu Retroactive blends tapioca starch, bamboo powder and kaolin to absorb oil without residue. K18 AirWash is a non-aerosol spray you shake first, and amika Perk Up is talc-free. Hair by Sam McKnight Lazy Girl is a light mist that stretches the time between washes while giving lift and hold. Living Proof PhD absorbs oil, sweat and odor while adding body.

Finish with Living Proof Full if your hair is fine and straight to wavy, since it is built for that texture. What I would skip: a heavy conditioner on the roots the day you plan to use fibers. Keep conditioner to the lengths.