This chapter addresses some of the novel physical features of the response and dynamics of homonuclear and heteronuclear clusters in ultraintense laser fields, which pertain to new mechanisms of cluster extreme multi-electron ionization, the consequences of the interaction of an ultraintense laser with a spatially confined cluster, the dramatic effects of nuclear fusion driven by cluster Coulomb explosion, the implications of Coulomb instability of highly multicharged clusters, etc. Ultraintense table top lasers are characterized by a maximal intensity of ∼1020 Wcm-2, which constitutes the highest light intensity on the earth. Novel features of light-matter interactions emerge from the interaction of clusters with ultrashort and ultraintense laser fields. The modem research area of femtosecond cluster dynamics on the time scale of nuclear motion is transcended by moving toward attosecond-femtosecond electron dynamics in ultraintense laser fields. The response of clusters to ultraintense lasers induces well characterized ultrafast dynamics of electrons and of ions in these large finite systems.