This study presents the extension of attosecond metrology to condensed-matter systems, enabling real-time observation of electron dynamics on the attosecond timescale. The researchers used attosecond pulses to probe photoelectron emission from single-crystal tungsten, revealing a delay of approximately 100 attoseconds between photoelectrons from localized core states and delocalized conduction-band states. This delay occurs during electron transport to the surface, demonstrating the capability of attosecond spectroscopy to capture fundamental electronic processes in solids. The technique combines photoemission spectroscopy with attosecond temporal resolution, allowing for time-domain insights into electron transport. By using a waveform-controlled, few-cycle laser pulse as a probe, the researchers achieved subfemtosecond resolution. The method involves measuring the energy and momentum of photoelectrons emitted from the surface, with the streaking effect of the NIR pulse enabling time-resolved measurements. The study shows that attosecond photoemission spectroscopy can provide detailed information about charge transfer, screening, and collective electronic motion in solids. The results highlight the potential of this technique for investigating a wide range of processes in solid-state and surface science. The researchers also developed a quantum mechanical model to reconstruct the measured spectra, supporting the conclusions drawn from the analysis of the data. The findings demonstrate the successful extension of attosecond metrology to condensed-matter systems, offering a powerful tool for studying electronic dynamics in solids. Future measurements may determine absolute emission delays by comparing results with gas-phase ATR data. This approach could ultimately reveal the intermediate processes leading to photoelectron ejection, providing new insights into electronic behavior in materials.This study presents the extension of attosecond metrology to condensed-matter systems, enabling real-time observation of electron dynamics on the attosecond timescale. The researchers used attosecond pulses to probe photoelectron emission from single-crystal tungsten, revealing a delay of approximately 100 attoseconds between photoelectrons from localized core states and delocalized conduction-band states. This delay occurs during electron transport to the surface, demonstrating the capability of attosecond spectroscopy to capture fundamental electronic processes in solids. The technique combines photoemission spectroscopy with attosecond temporal resolution, allowing for time-domain insights into electron transport. By using a waveform-controlled, few-cycle laser pulse as a probe, the researchers achieved subfemtosecond resolution. The method involves measuring the energy and momentum of photoelectrons emitted from the surface, with the streaking effect of the NIR pulse enabling time-resolved measurements. The study shows that attosecond photoemission spectroscopy can provide detailed information about charge transfer, screening, and collective electronic motion in solids. The results highlight the potential of this technique for investigating a wide range of processes in solid-state and surface science. The researchers also developed a quantum mechanical model to reconstruct the measured spectra, supporting the conclusions drawn from the analysis of the data. The findings demonstrate the successful extension of attosecond metrology to condensed-matter systems, offering a powerful tool for studying electronic dynamics in solids. Future measurements may determine absolute emission delays by comparing results with gas-phase ATR data. This approach could ultimately reveal the intermediate processes leading to photoelectron ejection, providing new insights into electronic behavior in materials.