Hepatobiliary malignancies-principally hepatocellular carcinoma (HCC) and cholangiocarcinoma (CCA)-are highly aggressive and often diagnosed at advanced stages. Curative-intent liver resection remains the standard for resectable disease; however, postoperative outcomes depend on an adequate functional future liver remnant (FLR). Associating Liver Partition and Portal Vein Ligation for Staged Hepatectomy (ALPPS) induces rapid FLR hypertrophy and has expanded resection eligibility compared with conventional two-stage hepatectomy by shortening the interval to definitive resection. Key uncertainties persist regarding the quality of ALPPS-induced regeneration and its relationship to long-term oncologic outcomes, including recurrence and metastasis. This observational study enrolls patients deemed suitable for ALPPS at Peking Union Medical College Hospital. Perioperative care follows institutional standards; no therapeutic procedures are altered for research purposes. The investigators will collect clinically available liver tissue and relevant medical data obtained during standard surgical care to characterize cellular and molecular programs of regeneration across the ALPPS stages. High-throughput profiling-including single-cell and spatial transcriptomics-will be used to define cell-type composition, transcriptional states, and signaling pathways associated with regeneration. The primary objective is to describe cellular and gene-expression changes in regenerating liver induced by ALPPS. Secondary objectives include exploring associations between regenerative quality and short- and long-term clinical outcomes. Findings are expected to inform potential therapeutic targets and strategies to enhance safe regeneration and improve postoperative prognosis.