  The Weak Equivalence Principle (WEP), stating that two bodies of different
compositions and/or mass fall at the same rate in a gravitational field
(universality of free fall), is at the very foundation of General Relativity.
The MICROSCOPE mission aims to test its validity to a precision of $10^{-15}$,
two orders of magnitude better than current on-ground tests, by using two
masses of different compositions (titanium and platinum alloys) on a
quasi-circular trajectory around the Earth. This is realised by measuring the
accelerations inferred from the forces required to maintain the two masses
exactly in the same orbit. Any significant difference between the measured
accelerations, occurring at a defined frequency, would correspond to the
detection of a violation of the WEP, or to the discovery of a tiny new type of
force added to gravity. MICROSCOPE's first results show no hint for such a
difference, expressed in terms of E\"otv\"os parameter
$\delta(Ti,Pt)=[-1\pm{}9{\rm (stat)}\pm{}9{\rm (syst)}] \times{}10^{-15}$ (both
1$\sigma$ uncertainties) for a titanium and platinum pair of materials. This
result was obtained on a session with 120 orbital revolutions representing 7\%
of the current available data acquired during the whole mission. The quadratic
combination of 1$\sigma$ uncertainties leads to a current limit on $\delta$ of
about $1.3\times{}10^{-14}$.
