I am new to both R and Bioconductor. I was going through available documentation and found the data set golubTrain. It contains ALL AML data set og Golub et al.(1999). After close examination I found this object contains not only the ALL AML expression data (original file data_set_ALL_AML_train.txt ) information on RNA samples (original file table_ALL_AML_samples.txt ) and some other information. I was wandering, how these type of objects, which contain information from multiple sources are generated from original data files. Thanks Dibakar Ray