The application of radioisotopes in the fields of condensed matter, materials science and biophysics has become one of the key activities at ISOLDE, the radioactive ion beam facility at CERN. Over the years, many radioactive probe techniques such as Emission Mössbauer Spectrocopy (EMS), Perturbed Angular Correlation (PAC) spectroscopy, Emission Channeling with Short-Lived Isotopes (EC-SLI), β-detected Nuclear Magnetic Resonance (β-NMR), radiotracer diffusion, radiotracer Photoluminescence (PL) spectroscopy, and radiotracer Deep Level Transient Spectroscopy (DLTS) have all been successfully applied using long- and short-lived radioisotopes produced at ISOLDE. Besides applications in solid state physics for the characterization of semiconductors and oxides, and in surface physics, recently biophysics and soft matter are playing an increasing role. In this talk, we will review these techniques and some recent highlights, from well-established research activities on doping of semiconductors , to emerging applications of these techniques in the context of biophysics  and quantum materials. We will also discuss potential opportunities for future radioactive ion beam facilities.
 U. Wahl et al., “Lattice location of Mg in GaN: a fresh look at doping limitations”. Physical Review Letters 118, 095501 (2017).
 S. Chakraborty et al., “Nanosecond Dynamics at Protein Metal Sites: An Application of Perturbed Angular Correlation (PAC) of γ-Rays Spectroscopy”. Accounts of Chemical Research 50, 2225 (2017).