Runtime Status
The runtime status bar at the bottom of the screen shows information about what your code is doing or has done.
While a cell is executing it shows what code is currently being executed:
Each section here responds to a stack frame and clicking on each will open the source code which is being executed. Here it's calling into pandas' read_csv which then calls into _read. For long-running cells this can be used to give an idea of where time is being spent.
Sometimes the stacks can get quite deep and it can be difficult to read what is happening. When this occurs the expand arrow on the left can be used to see all of the frames:
While executing code you may also see a small green arrow beside the cell- this indicates the line of code which is currently being executed:
Colab's variable inspector allows viewing information about the variables declared in your program's global scope and tracking progress of executing code.
The variable inspector can be opened from the 
button in the toolbar to the left.
Once it's open it will populate with the values of all global variables, including the type and shape and value.
While your program is running variables can also be displayed inline in the code editor:
