There are approximately 21 different types of trace elements in the human body. However, the exact number is unknown, and ongoing research continues to adapt this list. Each of the trace elements has different roles and functions within the body, and a deficiency or excess may lead to various clinical manifestations.  In addition to the nutritionally essential trace elements, there are a variety of probably essential elements and potentially toxic elements. These classifications are largely based on suggestive and ongoing research. The probably essential elements include manganese, silicone, nickel, boron, and vanadium.  Meanwhile, the potentially toxic elements include fluoride, lead, cadmium, mercury, arsenic, aluminium, lithium, and tin.