1.	A brief historical context of knowledge and use of keratin based-materials
2.	Keratin’s structure and chemical toolset
3.	Sustainability and safety assessment
4.	Keratins extraction
4.1.	Oxidative and reductive extraction
4.2.	Steam explosion extraction
4.3.	Extraction with Ionic liquids and deep eutectic solvents
5.	Keratin sources and their distinctions
6.	Keratin-based biomaterials
7.	Keratin associations with other polymers
7.1.	Keratin associations with synthetic and biosynthetic thermoplastics
7.1.1.	Polyolefins
7.1.2.	Polyethylene glycol (PEG) and Polyethylene oxide (PEO)
7.1.3.	Poly(ethylene imide) (PEI)
7.1.4.	Polyacrylates, polyacrylonitrile (PAN) and polyacrylamide (PAM)
7.1.5.	Polyvinyl chloride (PVC)
7.1.6.	Polyvinyl alcohol (PVOH)
7.1.7.	Polyamide-6 (PA6)
7.1.8.	ε-Polycaprolactone (PCL)
7.1.9.	Polylactic acid (PLA)
7.1.10.	Polyhydroxyalkanoates (PHA)
7.1.11.	Thermoplastic polyurethanes (TPU) and polyurea-urethanes (TPUU)
7.2.	Keratin associations with elastomers and thermosets
7.2.1.	Butadiene copolymer rubbers
7.2.2.	Epoxy resins
7.2.3.	Urea-formaldehyde resins
7.2.4.	Phenol-formaldehyde resins
7.3.	Keratin associations with natural polymers and fibres
7.3.1.	Keratin associations with carbohydrates
7.3.1.1.	Cellulose
7.3.1.2.	Chitosan
7.3.1.3.	Alginate
7.3.1.4.	Starch
7.3.2.	Keratin association with other proteins
7.3.2.1.	Collagen and gelatine
7.3.2.2.	Soy and wheat protein
7.3.2.3.	Silk fibroin
7.3.2.4.	Associations between different keratin sources
8.	Conclusions and outlook
Author Contributions
Conflicts of Interest
References