If you are using Salesforce Enterprise or Unlimited edition, Joined Report has been introduced sometimes back, with some limitations, slow performance, and need some improvements. But, in some business cases, we can take advantage of using this 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 standards 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 report 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 a new block with a different type by clicking the "Add Report Type" button, and it will create a new block and users can group the "common fields".
But, how we can have multiple blocks with the same object? Easy.... just drop a field at the right of the last block. See this video on Youtube.