To create the tear drop:
Draw a circle.
Open the DynamicSketch Panel - Window > Astute Graphics > DynamicSketch.
Ensure you have the Ability to edit and continue paths... button toggled on.
As you move the DynamicSketch Tool closer to your selected path, you will see a little infinity icon appear, this shows that DynamicSketch is going to join onto, and continue editing this path.
Draw the tear drop shape out, using part of the circle as your guide.
Optionally, add some highlights with lighter colored eclipses.
Select all the objects and group them together.
To fill a space with tear drops:
Draw the rectangle which you will fill with the tear drops.
Select both the tear drop group and the rectangle.
Open the Space Fill panel - Window > Astute Graphics > Space Fill.
Click the Make button.
Space Fill will now fill the rectangle with the objects as set out in the parameters in the panel.
You can adjust the live features including uniformity, size rotation, multiplication and release/expand in the panel.
Click the Randomize button to cycle through different Seeds.
If you want to stop the Space Fill, click the Release button.
If you are happy with your Space Fill and want to expand the shapes into multiple vectors, click the Expand button.