If you are using Salesforce Enterprise or Unlimited edition, joined report has been introduce sometimes back, with some limitations, slow performance and need some improvements. But, in some business case, we can take advantage using joined report.
The joined report format lets you view different types of information in a single report. A joined report can contain data from multiple standard or custom report types.
To get started with joined reports, create a new or edit an existing report in report builder, click the Format drop-down, and choose Joined. Most of the things you can do with summary or matrix reports you can also do with joined reports. For example, you can find, add, and remove fields; summarize fields; and run and save reports. You can show a joined report that includes a chart on a dashboard.
We can easily add new block for different type by click "Add Report Type" button, and it will create new block and user can group the "common fields".
But, how we can have multiple blocks with same object? Easy.... just drop a field at the right of the last block. See this video in Youtube.