A developmental biologist studies the processes that form and organize living bodies. Experiments on cell fate, signaling and morphogenesis connect changes in genes or environment to specific developmental outcomes. Comparing different organisms also reveals how developmental processes change through evolution.

A tissue organization with cells dispersed through extracellular matrix, rather than arranged as a continuous polarized epithelium. Mesenchymal populations differ in origin and developmental potential.

Formation, regionalization and maturation of the intestine, including its epithelial surface, supporting tissues and renewing cell populations.

Information allowing a cell to respond according to its location within a developing or regenerating structure. Establishing a positional value and interpreting it as a differentiated outcome are distinct steps.

Replacement of lost biological structures through organized growth and differentiation. Recovery of mass alone need not demonstrate restoration of the original pattern or function.

A population of cardiac progenitors that contributes cells to the developing heart after initial heart-tube formation. Retaining a proliferative reservoir allows progressive addition of differentiated myocardium.

The inner endothelial lining of the heart, which also provides developmental signals to neighbouring myocardium.

The outer tissue layer covering the heart, with developmental contributions to supporting cells and signals affecting myocardial and coronary development.

Neural development forms and organizes neurons, supporting cells and their connections. It includes precursor production, specification of cell types, migration, axon guidance and later changes in synaptic connectivity. Making the right number of cells and connecting them appropriately are distinct developmental requirements.

The ability of a cell or tissue to respond to an instructive signal at a particular stage and location. The same signal can have different effects after competence changes.

Skin development forms the epidermis, underlying supporting tissues and appendages such as hair follicles or feathers, depending on the lineage. Interactions between an epithelium and underlying mesenchyme help specify where appendages arise and how they grow.

Patterning is not just a list of expressed genes: changes in cell movement, tissue forces and local signaling can affect spacing and shape. A feather placode provides a localized precursor in which molecular identity and physical cell aggregation can be studied together.

Lung development builds the conducting airways and the thin exchange surface needed for breathing after birth. Growth and branching must be coordinated with cell differentiation, blood vessel development and preparation for air-filled function.

Mechanical conditions are part of the developmental signal. Live imaging and force perturbations linked fetal breathing movements and fluid loading to differentiation of type I alveolar cells, while local growth-factor responses helped other progenitors retain type II alveolar cell identity. This connects cell shape and tissue forces to acquisition of gas-exchange function.^[ref]

The timing and ordering of specification, differentiation, tissue movement and maturation. Equal chronological age need not imply equal developmental stage after perturbation.

Replacement of one position-specific developmental identity by another. Demonstrating it requires positive evidence for the alternative identity as well as loss of the original features.

Heart development produces the pumping organ, its chambers, lining and supporting structures through coordinated differentiation and morphogenesis. The early heart tube changes shape through cardiac looping and receives further cellular contributions; changes in shape, cell number and cell identity are separable processes.

In zebrafish, fluorescent developmental-timing assays and a photoconvertible fluorescent protein distinguished early differentiation from later addition at the arterial pole of the heart. These experiments showed why growth of the heart cannot be explained solely by division of already differentiated cardiac cells.^[ref]

Formation and differentiation of plant tissues and organs, continuously influenced by internal state and the environment.

Attachment and embedding of a mammalian conceptus in maternal tissue. Embryonic and extraembryonic tissues undergo coordinated morphogenesis during this transition.

The transition from predominant reliance on maternally supplied products to zygotic gene expression, accompanied by regulated turnover or redeployment of maternal molecules.

A representation of a finite set of bounded nonnegative integers by a binary word: bit $i$ is 1 exactly when $i$ belongs to the set. Bitwise AND, OR, and XOR implement intersection, union, and symmetric difference. A large integer can store the whole word when the programming language provides arbitrary-precision integers.

A binary tree organizing a fixed sequence into recursively subdivided contiguous intervals. Each node stores an aggregate for its interval. Range queries and point updates visit logarithmically many nodes; range-update variants store additional information such as a coverage count to maintain the length of a union of active intervals.