The modern idea of putting something on your scalp to grow hair began by accident. In the 1970s, minoxidil was a pill for high blood pressure, and doctors noticed that some patients taking it grew more hair. In 1988 the FDA approved a topical version as Rogaine, the first drug the agency endorsed for male pattern baldness, according to the Associated Press. A lower dose for women followed in 1991.

None of the best hair growth serums in this edit are minoxidil. They are cosmetic serums, which is why the boxes say thicker-looking, fuller-looking, less shedding and more density. That wording matters. A drug is approved to regrow hair. A cosmetic serum is allowed to improve how your hair and scalp look and feel, and the better ones back that up with clinical testing.

What they use instead is a mix of peptides, caffeine, plant stem cells and patented actives like Redensyl, Procapil, Baicapil and Capixyl. You will see those names over and over below.

The first grid is scalp serums for thinning hair. The second is more density treatments, including a few from newer brands. My tip: take a photo of your part line in the same light before you start, because every brand here talks in months, and you will not remember what day one looked like.

The Ordinary Multi-Peptide Serum for Hair Density is the one most people start with, and for good reason. It stacks Redensyl, Procapil and Baicapil in one bottle, and it is the least fussy formula here. Vegamour GRO Hair Serum is the clean, vegan option, with turmeric, caffeine and a red clover blend, and the brand says it reduces signs of shedding in about 90 days.

Kérastase Genesis is a little different. It targets breakage, which the brand calls a primary contributor to hair fall, so it suits hair that snaps from heat and brushing more than hair that sheds from the root. Living Proof Scalp Care Density Serum adds an anti-grey complex, which makes it the pick if you are thinning and greying at the same time.

Caudalie Hair Density Serum is aimed at thinning linked to stress, seasonal changes and aging, and it has the highest star rating in this grid. Nécessaire The Scalp Serum pairs 5% Capixyl with hyaluronic acid, dries fast and leaves no residue. Dr.FORHAIR Folligen is the Korean serum that went viral for the part line and hairline. Philip Kingsley Density Preserving Scalp Drops use azelaic acid, pyridoxine and zinc PCA to keep follicles healthy and the scalp less oily, and the brand says they suit sensitive skin.

What I would skip: layering two of these at once. Pick one, use it every day for three months, and then decide.

This grid leans on newer science and a few bolder claims, so read the fine print.

Augustinus Bader The Scalp Treatment uses the brand's Trigger Factor Complex, and the brand reports clinical gains in hair thickness, strength and count. Agent Nateur holi (growth) 84 is named for its 84-day timeline and pairs Redensyl with Follicusan, a milk protein, plus rosemary. Virtue Flourish Density Booster is a scalp spritz built around the brand's Alpha Keratin, made for mild to moderate thinning.

Act+Acre 2% Stem Cell Scalp Serum uses apple stem cells and is fragrance free, which I like for a sensitive scalp. Verb Density Peptide Scalp Serum is a lightweight serum with ginseng root and niacinamide, and it is a gentle place to start. K18 FutureIQ is a nightly serum for graying, shedding and scalp aging, and the brand says 70% of testers showed fewer grays.

Davines Energizing Superactive is the one aimed at hair loss linked to androgenic factors, with mung bean and crimson clover extracts. indē wild Moonlight Growth is water based and uses the same Redensyl, Procapil and Baicapil trio as the first grid.

A pairing tip: apply any of these to a clean, dry scalp in sections, then massage for a minute. The massage spreads it and makes the habit stick.

What I would skip: expecting a serum to fix sudden, patchy or heavy shedding. That is a doctor visit, not a shopping trip.

I think the best hair growth serums earn a spot in your routine as long as you know what you are buying. They make hair look thicker, several help with shedding, and a few have clinical data behind them. They are not minoxidil, and they do not claim to be. Choose by your main problem: shedding, breakage, greying or a dry scalp. Use one daily for three months, compare your photos, and see a dermatologist if the shedding is sudden or heavy.