Low-dimensional materials" refers to a new class of material with reduced dimensionality, i.e., with one or more physical dimension(s) constrained to the nanometer scale. Two-dimensional (2D) nanosheets, one-dimensional (1D) nanotubes, and zero-dimensional (0D) fullerenes represent typical examples of such materials. When compared to three-dimensional (3D) bulk substances, low-dimensional structures are anticipated to exhibit new properties due to quantum confinement and/or surface and

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... al effects. Therefore in recent years, materials scientists have drawn particular attention to these nanosystems to make sense of their unusual physical and chemical properties that can promote novel applications in engineering. Boron nitride (BN) low-dimensional materials are among the most promising inorganic nanosystems explored so far. BN is a chemical compound, consisting of equal numbers of boron (B) and nitrogen (N) atoms, which is not found in nature and is therefore produced synthetically. BN is isostructural to carbon (C) and exists in various crystalline forms. The hexagonal form (h-BN) is analogous to graphite with a layered structure. Four years after the identification of C nanotubes (CNTs) 1 , BN nanotubes (BNNTs) were successfully synthesized in 1995 2 . Subsequently other 1D BN nanomaterials such as nanowires, nanoribbons, nanofibers, and nanorods were synthesized 3-6 . Moreover, inspired by C 60 buckyballs 7 , 0D nested and single-layered octahedral BN fullerenes were produced in 1998 8,9 . In addition, after the rise of graphene in 2004 10 and the research progress on layered 2D nanostructures, free-standing 2D BN flakes were peeled off from a BN crystal in 2005 11 . However, the initial growth of BN nanosheets (BNNSs) in the form of so-called nanomeshes on metallic substrates had been reported a year earlier 12 . Structural models of 0D, 1D, and 2D BN nanomaterials are illustrated in Fig. 1. In this review, a concise research history of low-dimensional boron nitride (BN) nanomaterials followed by recent developments in their synthesis, morphology, properties, and applications are presented. Seventeen years after the initial synthesis of BN nanotubes, research on BN nanomaterials has developed far enough to establish them as one of the most promising inorganic nanosystems. In this regard, it is envisaged that the unique properties of low-dimensional BN systems, such as superb mechanical stiffness, high thermal conductivity, wide optical bandgap, strong ultraviolet emission, thermal stability and chemical inertness will play a key role in prospective developments.