To make essential oils, it needs to be extracted from the plant. This can be done through expression and distillation. Expression, also referred as cold pressing, expression is method used to extract oils from citrus fruits like lime, orange, tangerine, lemon, and bergamot. In the past, expression doesn't require any sorts of tools except for a sponge. After soaking the citrus rind or zest, it will be pressed against the sponge repeatedly to absorb the oil. The sponge will then be squeezed over a container to catch the oils and allow it to separate from its juices. After a few hours, the oils will be siphoned off and bottled. A modern type of expression involves using a blender-like device that's equipped with spikes. Once the citrus zest, rind, or peel is placed into the device, it will rotate and prod and prick the citrus until the oils are released. Oil will be collected at the bottom of the device and bottled immediately.