This lecture is divided into two part: tissue/cell engineering and biosensors. The goal of the first part is to give an introduction to the nanoscale sensibility of living, to the extreme sophistication of multi-level biologic assembly. The utilization of micro- and nanotechnologies for probing, stimulating or analyzing the cell and tissue behavior, are described in the domains of biomaterials, mecanobiology, molecular biology and personal medicine. The second part introduces the main concepts related to the design, the fabrication and the utilization of microsystems for molecular analysis in complex environments, liquid or gaseous. Such systems include sensors and biosensors, i.e., systems for the detection of certain chemical species, as well as biochips, which are devices for simultaneous multi-factor analysis. The course shows how the fundamental notions in the relevant scientific domains (physical chemistry of interfaces, biochemistry, physical measurements, ...) must be articulated in a coherent way, from the conception of biochips and their fabrication, to the interpretation of the resulting data, in order to achieve an analytical performance that is best adapted to the issue under investigation. We will discuss examples from the domain of academic research as well as commercialized systems, for applications related to health and environment.