The search for complex organic molecules (COMs) in the interstellar medium (ISM) has revealed chemical species of ever greater complexity in various types of environment, even in cold or UV-illuminated regions where they were initially not expected. This search relies heavily on the progress made in the laboratory to record and characterize their rotational spectra. Besides, our understanding of the chemical processes that lead to molecular complexity in the ISM builds on astrochemical numerical simulations that use chemical networks fed by laboratory and theoretical studies. On the observational side, the advent of the Atacama Large Millimeter/submillimeter Array (ALMA) and the expansion of the IRAM Plateau de Bure Interferometer now called NOEMA have recently opened a new door to explore the molecular complexity of the ISM. Thanks to the high angular resolution they can achieve, the spectral confusion of star-forming cores can be reduced, and their increased sensitivity allows astronomers to detect molecules of low abundance that could not be probed by previous generations of telescopes. The complexity of the molecules detected recently manifests itself not only in terms of number of their constituent atoms but also in their molecular structure. I will discuss results on molecular complexity in the ISM delivered by recent ALMA and NOEMA surveys.