1. Create a new document and a new shape
In Illustrator, create a new document that uses pixels as the unit of measurement. Select the Rounded Rectangle tool from the toolbar and click once in the artboard. Enter the values shown when the tool’s settings appear.
2. Rotate the shape 45-degrees
Select the shape and double-click the Rotate tool in the toolbar. Enter a value of 45 and click OK.
3. Reflect and copy the shape
Keep the shape selected and double-click the Reflect tool (keyboard shortcut of O; the letter not the number) in the toolbar. Set the Axis to Vertical, enable Preview, then click Copy.
4. Move, Select, Divide
Select the shape shown and hit the Enter/Return key on your keyboard to display the Move options. Enter a value of -20 for Horizontal and click OK. You can move the shape over further for a more compact heart shape in the end.
Use the Selection tool to select both shapes. Open the Pathfinder panel (Window > Pathfinder) and click the Divide command.
With the shapes selected, go to Object > Ungroup. Click an empty area of the artboard then use the Selection tool to select the two lowest shapes. Hit the Delete key on your keyboard to get the heart shape below.
5. Unite, Color
Select the remaining three shapes and click the Unite command on the Pathfinder panel. This will fuse the three shapes into one.
Edit the colors of the shape to suit your needs.