Detecting and manipulating individual atoms with high fidelity is crucial in state-of-the-art quantum simulators, processors and atomic clocks. I this talk I will present recent results for our ytterbium tweezer platform, aiming to engineer many-body systems and novel clock protocols with single-particle resolution. In our experiment, we load a tweezer array from a narrow-line MOT operating in a five-beam (5B) configuration, so far demonstrated only for lanthanides. We image single atoms with a fast and low-loss single-atom imaging in optical tweezers without active cooling. Using a pulsed excitation scheme, we collect fluorescence on microsecond timescales, reaching single-atom discrimination fidelities above 99.9% and single-shot survival probabilities above 99.5%. Unlike conventional imaging protocols, our scheme does not induce parity projection in multiply-occupied traps, enabling us to achieve number-resolved single-shot detection of up to several atoms per tweezer. We utilize such atom-counting imaging to characterize the near-deterministic preparation of single-atom occupations, driven by blue-detuned light-assisted collisions. The near-diffraction-limited spatial resolution associated with our low-loss imaging enables atom number-resolved detection in dense arrays, opening the way to multiple site-occupancy readout in quantum gas microscopes. We can extend this technique to detect single and multiple atoms in free space for variable time of flights (TOFs), allowing us to perform TOF thermometry of single- or few- atoms ensembles and, in the near future, to measure fermionic and bosonic multiparticle correlations in mesoscopic ensembles.