If you are working with people who use MATLAB, they might sometimes pass you data as a HDF5 file. HDFView is a tool written in Java that can be used to view the contents of such files.

Installing it is easy:

$ sudo apt install hdfview

Open any .h5 file using HDFView and it will display the hierarchy of the contents as a tree on the left. Click on the tree items to view its properties in the bottom. Double-click on the tree items to view its content in the main window.

Tried with: HDFView 2.9 and Ubuntu 14.04