  Millisecond pulsars, like pulsars, have led to major advances in many areas
of astronomy and physics. The discovery in 2023 of a cosmological gravitational
wave (GW) stochastic background using millisecond pulsar timing arrays has
focused attention on the importance of millisecond pulsars, to both
multi-messenger astronomy and cosmology, and for identifying the origin of the
GW stochastic background, which is hypothesized to be due to supermassive black
hole binaries (SMBHBs). Unlike pulsars, however, for which the details of the
discovery are well-known, those of millisecond pulsars are not well known. In
particular, the details of the first crucial step in the discovery of
millisecond pulsars, namely the discovery of interplanetary scintillation (IPS)
in the radio source 4C 21.53, are known only to the author. This article
presents a first-hand account of this crucial first step, which resulted
ultimately in the discovery of millisecond pulses from this object. A brief
description of interplanetary and interstellar scintillation and scattering is
given in the Appendix.
