Photovoltaics has today become a mature industry and one of the main reasons of the tremendous growth in recent years is the continuous improvement in the performance and lifetime of PV modules. However, one of the main limitations in the improvement of the performance of commercialized PV devices is that the efficiency is getting closer and closer to the single-junction theoretical limit defined as the Shockley-Queisser (SQ) limit [1]. The development of new concepts to surpass the SQ limit is therefore a hot topic in PV research. Among the main candidate technologies (hot carriers, up-conversion and down-conversion, light concentration …), multijunction devices are the only concept which have surpassed the SQ limit by a wide margin. Multijuntion devices are therefore the most promising solution for industrialization in the near future, and the dominant multijunction design today is the tandem solar cell. In this presentation, after a description of the functional advantages of multijunction solar cells, we’ll review the current status of tandems. We’ll compare the different types of tandem cells according to design principles, and in particular subcell materials, and discuss the challenges to upscaling tandem PV. In particular, we’ll discuss recent advances in tandem cells with a Si bottom cell and examine perovskite/Si tandem cells with a recent record efficiency of 29.8%.