# `Z` axis - depth

The `z` axis in maths is mainly thought of as depth.

In all situations however, the `z` axis is always 90° (perpendicular) to the `x` axis and `y` axis.

A deep sleep (depth) is lots of Z's (Z-Depth)

**Example 1**

**Example 2**

**Example 3**

# `Z` axis - depth

The `z` axis in maths is mainly thought of as depth.

In all situations however, the `z` axis is always 90° (perpendicular) to the `x` axis and `y` axis.

A deep sleep (depth) is lots of Z's (Z-Depth)

**Example 1**

**Example 2**

**Example 3**