## 1 Discovering the CNT  
The architect of carbon nanotubes (CNT) is [PERSON], a Japanese physicist awarded with the prestigious Benjamin Franklin Medal in 2002 \"for the discovery and elucidation of the atomic structure and helical character of multi-wall and single-wall carbon nanotubes\" [1]. The formation of \"carbon needles\" of few nanometres in diameter suggested that the manufacture of engineered carbon structures should be possible on very large scales. This technical possibility brought a real enthusiasm in chemistry and several academic teams completed this discovery by proposing complementary procedures to elaborate tailored CNT. Simultaneously, Professor [PERSON] and leading colleagues from the Universite de Namur in Belgium described in _Science_ an unsuspected extrusion of a carbon tubule from a catalytic particle [2].  
These success stories had huge impact on the rapidly growing material and nanoscale science field. The physico-chemical characteristics (such as the very high thermal, electrical conductivity,tensile strength and stiffness) attracted the attention of scientists of different domains and the interest of many industrial sectors (mainly in electronics). The production of CNT then emerged from university confinement and was deployed on a larger scale in the early 2000s in spin-offs and newly-built industries as Nanocyl in Belgium. However, this craze was short-lived. The discovery of their toxicity (see below), the difficulty of large-scale synthesis and their high selling price explain slowdown in global demand for CNT during that disillusionment period.  
However, industrial production of CNT is now experiencing a revival of interest. Plastic and battery suppliers recently assimilated the major interest of CNT and revived the market. Today, the management of the harmful effects of CNT is no longer be considered as an impassable barrier. Indeed, safe-by-design approaches now offer tailored CNT characterized by weak toxicity and limited health concerns [3, 4]. Several recent reports mention that the worldwide market for CNT is estimated to grow from 5 billion U.S. dollars in 2018, to 10 billion by 2023 and 15 billion in 2026. During this forecast period, a CAGR (Compound annual growth rate) of 20% is expected. The Yano Research Institute Ltd. (Tokyo, Japan) released a report predicting a global CNT market of 4000 tons by 2023, representing a compound annual growth of 13% (2250 tons in 2018 when considering the global CNT market) [5].  
Chemical vapor deposition (with or without catalysts) represents the main synthetic technique, and accounts for more than 70% of the global production. Currently, efficient production and declined prices for CNT make these nanomaterials more available and affordable [6]. Multi-walled CNT dominate the market and their increasing applications concern battery additives and plastic parts [7, 8]. CNT also hold absorbent potential for organic wastewater treatment or emerging contaminant because of their high specific surface area and mesoporous structure [9, 10, 11]. The recent ability to functionalize CNT or control their growth and assembly [12] gives rise to the development of new biomedical applications, including tissue growth and drug delivery [3, 13]. For instance, CNT-based materials permit the elaboration of layered cell architectures for embryonic stem cell and spheroid expansion during tissue regeneration [14, 15].