I review the recent instrumental progresses which allow to directlyobserve galaxy properties at the earliest epochs of the Universe.This leads to the derivation of fundamental quantities, such as theepoch of massive galaxy formation or the universal history of heavyelement formation. Star formation history shows a gradual declinesince the last 8-9 Gyr. The bulk of present-day stellar mass and metalcontent was formed at redshifts 0.5 to ~3, which is consistentwith hierarchical scenarii of galaxy formation. The numerousuncertainties related to these determinations are emphasized,including those linked to stellar physics.