Natural fibres -- both lignocellulosic and protein -- are renewable and biodegradable. They are characterised by good air permeability, hygroscopicity, and do not release harmful substances. They have been well-known to mankind for more than 9,000 years. Most of the lignocellulosic fibres from plants and animals such as cotton, flax, hemp, jute, kenaf, sisal, ramie, curaua, pineapple, bamboo, coir, sheep, alpaca wool and silk can be extracted, processed, modified, functionalised, and used in the production of textiles (woven, knitting, nonwoven, technical, and 3D textiles), and as reinforcement for more environmentally friendly composites. Special treatment and functionalisation methods such as degumming, enzymes, ultrasounds, plasmas, coronas, liquid ammonia, flame retardant treatments and protection against biodeterioration provide new promising features and properties for all natural fibres. The production of natural fibres is expected at the level of about 40 million tons/year in the middle of the 21st century. Global fibre production was 95 million tons in 2015 and it is estimated to grow 3% annually, reaching 122 million tons in 2025. Some natural fibres are susceptible to dyeing by natural dyestuffs, UV resistant and can be easily protected against flammability. Natural fibres and fabrics after special functionalisation by MOFs (Metal-organic Frameworks), POMs (Polyoxymetalates) and dendritic polymers will play an important role in the near future not only in defenceand military apparels, but in very effective filter materials as well. The book contains (in eleven chapters with eleven sub-chapters) topics about: Cotton as a dominant natural fibre; the novel challenge for bast fibres; flax and hemp; breeding and cultivation of flax in China (the biggest processor of flax and hemp in the world); new emerging sources of lignocellulosic fibres, (ie: curaua and Daphnopsis fasciculata fibres from South America); the role of apparels based of natural fibres in human physiology; bioengineering as a driving force in natural fibres stabilisation and production growth; chemical and biochemical functionalisation and finishing of natural fibres, including treatment by dendritic polymers; and alpaca fibre production, characteristics and use. Composites based on natural fibres; bio-based composites; poly( -caprolactone)/poly(lactic acid)/oil palm fibre composites; plant fibres: renewable reinforcing fillers in polyolefins biocomposites; and use of palm fibres reinforced in polymer matrices. Natural lignocellulosic raw materials as both a source of nanocellulosic fibres and of further information about natural fibres. The book presents the latest research data about new and emerging areas of natural fibres in the scope of production, processing and its applications.