Resumen: Carbon nanotubes undoubtedly take a leading position in nanotechnology research owing to their well-known outstanding structural and electronic properties. Inspired by this, hybrid and functionalized tubular structures have been constructed via several modification paths that involve the presence of molecules, generation of defects, and partial or full replacement of the carbon atoms, always maintaining a nanotube structure. The possibilities are countless. However, this review is mainly dedicated to giving a fundamental insight into the concepts behind wall modification, doping, and formation of a carbon nanotube structure. Theoretical concepts and experimental achievements ranging from carbon nanotubes with low B or N doping to the new physics behind boron nitride nanotubes are covered. Furthermore, special attention is devoted to the bulk and local characterization tools employed with these materials, their suitability and limitations. The theoretical approaches to describing the physical and chemical properties of heteronanotubes are objectively analyzed versus the materials available at this moment. Idioma: Inglés DOI: 10.1103/RevModPhys.82.1843 Año: 2010 Publicado en: REVIEWS OF MODERN PHYSICS 82, 2 (2010), 1843-1885 ISSN: 0034-6861 Factor impacto JCR: 51.695 (2010) Categ. JCR: PHYSICS, MULTIDISCIPLINARY rank: 1 / 79 = 0.013 (2010) - Q1 - T1 Financiación: info:eu-repo/grantAgreement/EUR/e-I3/ETSF-211956 Financiación: info:eu-repo/grantAgreement/EUR/FP6/IST-DNA-NANODEVICES-029192 Financiación: info:eu-repo/grantAgreement/EUR/FP6/NMP4-CT-2006-03350 Financiación: info:eu-repo/grantAgreement/ES/MEC/FIS2007-65702-C02-01 Tipo y forma: Article (Published version)