  In the past decade, optical vortex knots with axial dimensions on the order
of $10^2-10^5$ wavelengths ($\lambda$) have been implemented in the laboratory.
However, many potential applications require a drastic reduction on the the
size of these knots to the order of $\lambda$. In this work, we show the first
measurement of an optical vortex knot (trefoil) with an axial length of $1.99\,
\lambda$ contained within a volume ($x\times y\times z$) of $1.90\times
2.19\times 1.99 \, \lambda^3$. Prior to focusing, the laser light is linearly
polarized ($x$, horizontal) and we observe the knot in the dominant $x$
polarization component of the tightly focused field. We also observe the
transition of the trefoil knot to a couple of vortex loops via reconnection of
the vortex lines as we change the spatial scale of the angular spectrum
representation of the field.
