[en] Full text: Topological insulators (TIs) are a new class of materials characterised by linear gapless surface states, which emerge in the bulk band gap due to non-trivial topology of the band structure. These boundary states, protected from back-scattering because of their spin-polarized nature, make field effect transistors of topological insulators promising building blocks for future low-power electronics. Because of the gapless nature of the surface states, the only way to switch off these transistors is to induce a topological phase transition, i.e., transforming topological insulator to a trivial insulator. This topological phase transition can be induced by different ways: for example breaking the time reversal symmetry by introduction of a magnetic field or introduction of ferromagnetic order, or creating a band inversion through strain, electric field, etc. In this talk I will present work from my PhD in IISc, India, on directly probing such topological phase transition in a 3D topological insulator (Bi_1.6Sb_0.4Te₂Se) as a function of a magnetic field with universal conductance fluctuations. I will also highlight our recent endeavours at Monash University to engineer topological phase transitions in van derWaals heterostructures of topological insulators. (author)