Generally, e-textile is mainly segmented into three parts such as sensors, actuators, and control units [
126]; smart textiles are categorized as (i) passive smart textiles which sense only external stimuli [
27]; (ii) active smart textiles which sense reactions to the circumferential environmental condition [
127]; (iii) smart and intelligent textiles which sense, react, and adapt their attribute to the external situation [
127,
128]. Broadly, e-textiles and wearable electronics, thermo-regulating textiles, stimuli-responsive textiles, plasmonic textiles, and photonic textiles with individual branches are mainly mentioned as smart and intelligent textiles as illustrated in
Fig. 3A [
27,
126-
132]. All kinds of e-textile can be passive or active smart materials. E-textile and wearable textiles are prepared primarily based on the breathability, flexibility, resiliency, stability, and bending properties of textile materials. Also, other electronic properties of textiles can be attained
via the incorporation of nanomaterials such as graphene and carbon nanotube (CNT) into it [
133,
134]. The intersection of nanoelectronics with textiles suggests unique behavior for high-performance applications such as supercapacitors, electrostatic power generators, textiles batteries. Photonic textiles are integrated with polymeric optical fibers, light-emitting diodes, photoluminescent polymer-coated fibers, sensors, and thermochromic dye-coated yarns for changing the characteristics by altering emission frequency, colors, and design of emitted lights [
135]. Bragg fibers are one type of photonic fiber; prepared by making solid and hollow-core ringed by sporadic dielectric nanolayers with low and high reflective indexes [
136]. Plasmonic textiles were prepared by conformal deposition of metal nanoparticles by immersion of cotton fabric into the solution encompassed with nanoparticles (Ag, Au, and Pt) and followed by an
in-
situ synthesis system. Various colors in the fabric were created due to the diverse size and shapes of nanoparticles that were presented on the surface of cotton fabrics [
137]. Of late, gold-coated optical plasmonic fiber-based sensors have been used in smart textiles to detect dew creation, and this had been offered by Esmaeilzadeh
et al. [
138]. Generally, stimuli-responsive polymers are used in smart textiles to change their properties with surrounding environmental stimuli-deviation including light-responsive polymers, piezo-responsive polymers, pH-responsive polymers, thermal-responsive polymers, and moisture-responsive polymers. These kinds of polymers functionalize enormous attributes to smart textiles such as esthetic look, comfort, fantasy design with varied colors, wound tracking, smart wetting behavior, drug delivery system, and safeguard against extreme weather [
139,
140]. Currently, the application of nanotechnology in stimuli-responsive textiles exhibits better performance such as nanofiber-based shape memory polymer which can return to a permanent shape from a temporary shape by the effect of extraneous stimuli [
141]. Finally, thermo-regulating textiles are prepared by using phase change materials (PCMs) as they can change one physical condition to another to control the homogeneous temperature of textiles [
142]. Microencapsulated is the most widely used PCMS to apply on textile substrates for the formation of thermo-regulating smart textiles. Presently, nanomaterials such as CuO, TiO
2, Al
2O
3, and CNTs have been incorporated into PCMs to enhance thermal performance [
143]. However, electrical insulation can be utilized to prevent electric shorts, shocks, and fires from occurring when wearing conductive materials. This electrical insulation of the conductive textiles can be achieved by enclosing the conducting elements in an electrically insulating layer using techniques like core spinning or tubular intarsia knitting, or by encasing them in a water-resistant polymer [
144]. Intelligent clothing made of these above techniques has been portrayed in
Fig. 3B that could be used for multifunctional purposes.