E {top: 0; /* сверху */bottom: 0; /* снизу */text-align: center; /* горизонтально */vertical-align: middle; /* вертикально */}
<div class="poem"><div>буря мглою</div><div>небо кроет</div><div>вихри снежные</div><div>крутя</div></div>
.poem {overflow: hidden;height: 640px;}.poem div {float: left;}
.poem div:first-child {background: #090;}.poem div:last-child {background: #C00;}
.poem {display: flex;}
.poem {display: flex;flex-direction: row; /* по умолчанию */flex-direction: row-reverse;}
.poem {display: flex;flex-direction: column;}
.poem {display: flex;flex-direction: column-reverse;}
.poem {display: flex;justify-content: flex-start; /* по умолчанию */justify-content: flex-end;}
.poem {display: flex;justify-content: center;}
.poem {display: flex;justify-content: space-between;}
.poem {display: flex;justify-content: space-around;}
.poem div:nth-child(2) {order: 1;}
.poem div {order: 4;}
.poem div:nth-child(1) { order: 2 }.poem div:nth-child(2) { order: 1 }.poem div:nth-child(3) { order: 4 }.poem div:nth-child(4) { order: 3 }
.poem div {height: 250px;}
.poem {display: flex;align-items: flex-start; /* по умолчанию */align-items: flex-end;}
.poem {display: flex;align-items: center;}
.poem div:nth-child(1) {align-self: flex-start;}.poem div:nth-child(4) {align-self: flex-end;}
.poem {display: flex;}.poem div {margin: auto;}
.poem div {flex-grow: 1;}
.poem div {flex-grow: 1;}.poem div:nth-child(1) {flex-grow: 4;}
.poem div {width: 25%;}.poem div:nth-child(1) {flex-shrink: 4;}
.poem div {flex-grow: 1;}.poem div:nth-child(1) {flex-basis: 250px;}
.poem {display: flex;flex-wrap: nowrap; /* по умолчанию */flex-wrap: wrap;}
.poem {display: flex;flex-wrap: wrap-reverse;}
.poem {display: flex;align-content: stretch; /* по умолчанию */align-content: center;}
Только для многострочных блоков!
E {display: -webkit-box;display: -moz-box;display: -ms-flexbox;display: -webkit-flex;display: flex;}
E {-webkit-box-flex: 1;-moz-box-flex: 1;-ms-flex: 1;-webkit-flex: 1;flex: 1;}
E { -webkit-box-orient: vertical;-moz-box-orient: vertical;-ms-flex-direction: column;-webkit-flex-direction: column;flex-direction: column; }
E { -webkit-box-orient: vertical;-webkit-box-direction: reverse;-moz-box-orient: vertical;-moz-box-direction: reverse;-ms-flex-direction: column-reverse;-webkit-flex-direction: column-reverse;flex-direction: column-reverse; }
E { -webkit-box-orient: horizontal;-webkit-box-direction: reverse;-moz-box-orient: horizontal;-moz-box-direction: reverse;-ms-flex-direction: row-reverse;-webkit-flex-direction: row-reverse;flex-direction: row-reverse; }
E {-webkit-box-pack: justify;-moz-box-pack: justify;-ms-flex-pack: justify;-webkit-justify-content: space-between;justify-content: space-between;}
E {-webkit-box-align: center;-moz-box-align: center;-ms-flex-align: center;-webkit-align-items: center;}
E {-webkit-box-ordinal-group: 1;-moz-box-ordinal-group: 1;-ms-flex-order: 1;-webkit-order: 1;order: 1;}
Вадим Макеев, Opera Software
Презентация: pepelsbey.net/pres/flexbox-gotcha